How many drinks does it take to reach 0.08%?

By the equation, a 180 lb man crosses 0.08% at roughly 3.4 standard drinks with no time elapsed, and a 140 lb woman at roughly 2.1. Those figures fall as body weight falls and rise slightly for every hour that passes. They describe where the model crosses a legal line, not a quantity anyone can safely drink before driving — impairment of judgement, reaction time and divided attention is measurable from well below 0.08%, and the only safe amount before driving is none.

How long does alcohol stay in your system?

The body clears alcohol at roughly 0.015 BAC percentage points an hour, and that rate barely changes with how much you have drunk, so the decline is close to a straight line. An estimate of 0.08% therefore takes about five and a half hours to return to zero in the model, and 0.12% about eight. Nothing speeds this up — not coffee, not a cold shower, not food eaten afterwards, not exercise. Real elimination rates vary between about 0.010 and 0.025 points an hour, so the model's timing can be well out for an individual, and reaching zero in an equation is not the same as being unimpaired.

Is a blood alcohol calculator accurate?

No calculator can tell you your actual BAC — only a breath, blood or urine test measures it. Widmark is a 1932 population-average model that assumes every drink is fully absorbed, that your body composition matches a fixed ratio, and that your liver clears alcohol at exactly the average rate. It has no term for food, medication, illness, hydration, the menstrual cycle, drinking pace, or how large the pours really were. Individual results routinely land well above or below the estimate, which is why the number on this page must never be treated as a permission slip.

What counts as one standard drink?

In the United States a standard drink contains 0.6 fluid ounces — about 14 grams — of pure ethanol. That is a 12 fl oz beer at 5% ABV, a 5 fl oz glass of wine at 12% ABV, or a 1.5 fl oz shot of 80-proof spirits. The definition is about the alcohol, not the glass: a 16 fl oz craft pint at 7% ABV is about 1.87 standard drinks, a 24 fl oz malt liquor at 8% is over three, and a free-poured home cocktail is rarely one. Counting glasses instead of standard drinks is the single most common way people underestimate their own BAC.

What is the legal BAC limit in the United States?

For drivers aged 21 and over the per se limit is 0.08% in 49 states, the District of Columbia and the territories; Utah lowered its limit to 0.05% in December 2018. Commercial driver's licence holders are held to 0.04%, and every state has a zero-tolerance law for drivers under 21, typically set at 0.02% or at any detectable amount. Many states add mandatory penalties at 0.15% and above. All of these are legal thresholds, not safety thresholds — a driver can be arrested and convicted below the limit if an officer judges them impaired.

Why does the calculator ask for biological sex?

Only to pick the r value in the equation: 0.73 or 0.66. Widmark's r is a rough proxy for the share of body mass made up of water-rich tissue, because ethanol dissolves in water and not in fat. On average that share differs between male and female bodies, which is why the two constants exist. It is a body-composition input, not a statement about identity, and it is crude either way — two people of the same weight and the same recorded sex can sit well either side of the number the model uses.

Can you drive after one drink?

The safe answer is no. Impairment does not begin at a legal limit; measurable losses in judgement, divided attention and visual tracking appear from the first drink, well below 0.08% and below 0.05%. A calculator cannot tell you otherwise, because it cannot measure you — it applies an average to a rough description of what you drank. If you have had any alcohol, plan not to drive: use a taxi, a rideshare, public transport, a sober driver, or stay where you are.

Health

Blood Alcohol Calculator

Blood alcohol concentration is estimated with the Widmark equation, BAC% = (A × 5.14 / (W × r)) − 0.015 × H: the pure alcohol you drank, your body weight, a distribution factor, and the hours since your first drink. It is an estimate from a population average — it must never be used to decide whether to drive.

Your details

Biological sex

This only sets Widmark's r factor (0.73), a rough proxy for how much of your body is water-rich tissue. It is a body-composition input, not a statement about identity.

Body weight

Everything is converted to pounds internally

What you drank

Count servings, not glasses — a big pour is more than one drink.

Beer

12 fl oz · 5% ABV · 1 std

Wine

5 fl oz · 12% ABV · 1 std

Shot

1.5 fl oz · 40% ABV · 1 std

Craft pint

16 fl oz · 7% ABV · 1.87 std

Custom drink

8 fl oz · 13% ABV · 1.73 std

Volume (fl oz)ABV (%)

Hours since the first drink

Measured from the first drink, not the last

Estimated BAC

0.040%

Impairment begins3 drinks · 180 lb · 2 hr

Estimate only — never use it to decide whether to drive

Widmark is a population average. For any individual it can be wrong in either direction, and it cannot see food, medication, illness, how fast you drank, or how big the pours really were. The only amount of alcohol that is safe before driving is none. If you have been drinking, do not drive — take a taxi, a rideshare, transit, or stay put.

What is typically measurable here

Loss of judgement, altered mood and relaxation. Measurable decline in visual function and in the ability to divide attention between two tasks — the core skill driving demands.

Standard drinks

Pure ethanol

1.8 fl oz

Widmark peak

0.070%

Modelled clearance

−0.030%

Where the model goes from here

0h1h2h3h4h

Hour you entered 0.05% limit 0.08% limit

Estimated time until the model returns to 0.00%: 2 hr 42 min from now — 4 hr 42 min after the first drink. That is a property of the equation, not permission to drive, and not a time at which anything becomes safe or legal.

Try a scenario

One US standard drink = 0.6 fl oz of pure ethanol.

No sign-up · Free

Read this before the number

This is an estimate, and it is not a decision tool for driving

An estimate, not a measurement

Widmark is a population average built in 1932. For any given person on any given night it can be wrong in either direction, sometimes badly. Only a breath, blood or urine test measures blood alcohol.

Never use it to decide whether to drive

No number on this page means it is acceptable to get behind the wheel. The only amount of alcohol that is safe before driving is none. If you have been drinking, arrange a taxi, a rideshare, transit, a sober driver, or stay put.

A legal limit is not a safety limit

0.08% — and 0.05% in Utah, 0.04% for commercial drivers, effectively zero under 21 — are the points at which the law says an offence is proved. Impairment of judgement, reaction time and divided attention begins well below all of them, from the first drink.

There is no countdown to sober here

Where this page shows the estimate falling back to 0.00%, that is a property of the equation and nothing else. It is not a time after which driving becomes safe or legal, and it should not be planned around.

If someone is unresponsive, breathing irregularly, cold or clammy, or cannot be woken, treat it as suspected alcohol poisoning and call emergency services. Do not leave them to sleep it off. This page is general information, not medical or legal advice.

The basics

What is blood alcohol concentration?

Blood alcohol concentration is the mass of ethanol dissolved in a fixed volume of blood, written as a percentage. A reading of 0.08% means eight hundredths of a gram of alcohol in every hundred millilitres of blood. It is the number breath tests approximate, the number drink-driving law is written around, and the number the Widmark equation tries to predict from a description of what you drank. Two ideas carry the whole model.

BAC% = (A × 5.14 / (W × r)) − 0.015 × H

Alcohol spread through body water

Ethanol dissolves in water, not fat, so the same drink is diluted into whatever volume of water-rich tissue a body has. That is what W and r stand in for — the weight, and the fraction of it alcohol can spread into. A larger volume means a lower concentration from the same drink.

4 standard drinks · 180 lb · r 0.73 → peak 0.094%

a flat 0.015 %/hr

Elimination that ignores the level

Almost all alcohol leaves through the liver, and the enzymes doing the work are saturated at anything above a trivial dose. So the body clears a near-constant amount per hour rather than a percentage of what is there — the fall is a straight line, and nothing you can do makes the line steeper.

After 2 hours the model subtracts 0.030%, leaving 0.064%

Method

How to calculate BAC by hand

Four steps take you from a description of an evening to a number. The worked figures below follow a 180 lb man who has had four standard drinks over two hours.

1
Convert every drink to fluid ounces of pure ethanol
Multiply each serving's volume by its strength, then add them up. This total is A. A US standard drink is the reference point, so if you only had standard servings you can multiply the count by it directly.
A = 4 × 0.6 = 2.4 fl oz (56 g)
2
Take your body weight in pounds and pick r
W is body weight in pounds; convert from kilograms or stone first. r is Widmark's distribution ratio — a proxy for the share of your body that is water-rich tissue.
W = 180 lb · r = 0.73 · W × r = 131.4
3
Apply the Widmark fraction for the peak
Multiply A by the conversion constant and divide by W × r. This is the concentration before the liver has removed anything — the theoretical peak.
2.4 × 5.14 ÷ 131.4 = 0.0939%
4
Subtract the alcohol metabolised since the first drink
Multiply the hours elapsed, H, by the average elimination rate and take it off the peak. Count from the first drink, not the last, and floor the result at zero.
0.0939% − (0.015 × 2) = 0.064%

The same arithmetic for a 140 lb woman with two standard drinks over one hour gives a peak of 0.067% and an estimate of 0.052% — lighter body, lower r, half the alcohol, one hour of clearance.

Worked examples

Four sessions through the same equation

A beer night, wine with dinner, a run of shots, and a long mixed session. Switch tabs to watch the working change — and notice how often the number of glasses and the number of standard drinks disagree.

Four beers over three hours

A 180 lb man drinks four 12 fl oz beers at 5% ABV across three hours at a friend's place.

Given W = 180 lb, r = 0.73, H = 3 hr

4 × Regular beer: 4 × 12 fl oz × 5% = 2.4 fl oz ethanol

Total A: 2.4 fl oz ethanol = 4 standard drinks

Widmark peak: 2.4 × 5.14 ÷ (180 × 0.73) = 0.0939%

Subtract metabolism: 0.0939% − (0.015 × 3) = 0.0489%

BAC ≈ 0.049%

Impairment beginsmodel reaches 0.00% about 6 hr 16 min after the first drink

Four servings, four standard drinks — this is the one case where counting glasses and counting drinks give the same answer.

Every one of these is an estimate for an average person of that weight. None of them says anything about whether the person in the example could safely drive — the answer to that is always no once any alcohol has been consumed.

Standard drinks

What actually counts as one drink

The equation is fed in fluid ounces of pure ethanol, and the US standard drink is how that gets counted in practice: 0.6 fl oz — about 14 grams — of ethanol per serving. Three very different glasses hit it exactly, which is the whole point of the definition. Plenty of ordinary servings do not.

Serving	Size	ABV	Pure ethanol	Standard drinks	Notes
Regular beer	12 fl oz	5%	0.6 fl oz	1	A 12 fl oz can or bottle at 5% ABV — the serving the US standard drink is defined from.
Table wine	5 fl oz	12%	0.6 fl oz	1	A 5 fl oz pour at 12% ABV. Restaurant and home pours are routinely half again as large.
Spirits (80 proof)	1.5 fl oz	40%	0.6 fl oz	1	A 1.5 fl oz shot of 80-proof spirits, neat or as the base of a mixed drink.
Craft beer or IPA	16 fl oz	7%	1.12 fl oz	1.87	A 16 fl oz pint at 7% ABV — one glass, but close to two standard drinks.
Light beer	12 fl oz	4.2%	0.5 fl oz	0.84	Slightly under a standard drink, which is the entire point of the category.
Hard seltzer	12 fl oz	5%	0.6 fl oz	1	Engineered to land on the standard-drink definition, though 8% versions exist.
Malt liquor	24 fl oz	8%	1.92 fl oz	3.2	A single 24 fl oz can at 8% ABV is more than three standard drinks.
Fortified wine	3.5 fl oz	18%	0.63 fl oz	1.05	Port, sherry and vermouth are poured small because they are poured strong.
Mixed cocktail	4.5 fl oz	22%	0.99 fl oz	1.65	A martini or negroni is mostly spirit; a free-poured home cocktail is rarely one drink.

A 16 fl oz craft pint at 7% ABV is 1.87 standard drinks — order two and the count is already close to four.

Metabolism

How the body handles alcohol

Three stages, and the model only really represents the third. Understanding the first two is how you understand why a calculator can be so far out.

stomach → small intestine

Absorption

A small share of alcohol crosses the stomach wall; the great majority is absorbed in the small intestine. Anything that slows the stomach emptying — a meal, especially one with fat and protein — spreads that absorption out and lowers the peak. An empty stomach and a fizzy drink do the opposite.

total body water

Distribution

Once in the blood, ethanol distributes into the water throughout the body. Lean tissue holds far more water than fat does, so the same drink reaches a lower concentration in a body with more lean mass. This is the entire job of the r factor, and it is why the model is only ever approximate.

zero-order kinetics

Elimination

The liver does almost all of it, via alcohol dehydrogenase and then aldehyde dehydrogenase. Those enzymes saturate quickly, so clearance runs at a near-constant amount per hour rather than proportionally to the level. A few percent leaves in breath, sweat and urine, which is what makes a breath test possible.

0.015 %/hr — a 0.08% estimate takes about 5 hr 20 min to reach zero

Effect levels

What each BAC band looks like

The bands below describe what is typically measurable in laboratory and driving-simulator studies at each concentration. They are averages across people, not a prediction about any individual — and there is deliberately no green band, because no level here means it is acceptable to drive.

0.00% – 0.019%

Below 0.02%

Little measurable change on most laboratory tests, but this is an average across people, not a clean bill. Judgement and risk-taking can shift from the first drink, and the model cannot see that.

0.02% – 0.049%

Impairment begins

Loss of judgement, altered mood and relaxation. Measurable decline in visual function and in the ability to divide attention between two tasks — the core skill driving demands.

0.05% – 0.079%

Over Utah's limit

Reduced coordination and difficulty tracking moving objects. Steering degrades, response to emergency situations slows, and alertness and inhibition both fall.

0.08% – 0.149%

Over the US legal limit

Poor muscle coordination in balance, speech, vision, reaction time and hearing. Harder to detect danger; judgement, self-control, reasoning and memory are all impaired. Per se illegal to drive in 49 states.

0.15% – 0.299%

Severe impairment

Substantial loss of balance and muscle control, vomiting likely without a high tolerance, major loss of attention and of vehicle control. Many states treat this level as aggravated DUI.

0.30% and above

Medical emergency

Confusion, stupor and the range where alcohol poisoning occurs — suppressed breathing, loss of the gag reflex, loss of consciousness. Call emergency services rather than letting someone sleep it off.

Quick chart

BAC by drinks and body weight

The lookup people actually want: estimated blood alcohol concentration for every combination of body weight and number of US standard drinks, for both distribution ratios, with the hours elapsed adjustable. The last column of each table is the drink count at which the equation crosses the 0.08% legal limit.

Hours since the first drink

Estimated BAC by body weight and number of US standard drinks, before any metabolism is subtracted. Columns are standard drinks; a 16 fl oz craft pint counts as nearly two of them.

Male · r = 0.73

Estimated blood alcohol concentration for a male by body weight and number of US standard drinks, 0 hours after the first drink
Weight	1	2	3	4	5	6	7	8	9	10	To cross 0.08%
100 lb(45 kg)	0.042	0.084	0.127	0.169	0.211	0.253	0.296	0.338	0.380	0.422	1.9
120 lb(54 kg)	0.035	0.070	0.106	0.141	0.176	0.211	0.246	0.282	0.317	0.352	2.3
140 lb(64 kg)	0.030	0.060	0.091	0.121	0.151	0.181	0.211	0.241	0.272	0.302	2.7
160 lb(73 kg)	0.026	0.053	0.079	0.106	0.132	0.158	0.185	0.211	0.238	0.264	3
180 lb(82 kg)	0.023	0.047	0.070	0.094	0.117	0.141	0.164	0.188	0.211	0.235	3.4
200 lb(91 kg)	0.021	0.042	0.063	0.084	0.106	0.127	0.148	0.169	0.190	0.211	3.8
220 lb(100 kg)	0.019	0.038	0.058	0.077	0.096	0.115	0.134	0.154	0.173	0.192	4.2
240 lb(109 kg)	0.018	0.035	0.053	0.070	0.088	0.106	0.123	0.141	0.158	0.176	4.5
260 lb(118 kg)	0.016	0.032	0.049	0.065	0.081	0.097	0.114	0.130	0.146	0.162	4.9

Female · r = 0.66

Estimated blood alcohol concentration for a female by body weight and number of US standard drinks, 0 hours after the first drink
Weight	1	2	3	4	5	6	7	8	9	10	To cross 0.08%
100 lb(45 kg)	0.047	0.093	0.140	0.187	0.234	0.280	0.327	0.374	0.421	0.467	1.7
120 lb(54 kg)	0.039	0.078	0.117	0.156	0.195	0.234	0.273	0.312	0.350	0.389	2.1
140 lb(64 kg)	0.033	0.067	0.100	0.134	0.167	0.200	0.234	0.267	0.300	0.334	2.4
160 lb(73 kg)	0.029	0.058	0.088	0.117	0.146	0.175	0.204	0.234	0.263	0.292	2.7
180 lb(82 kg)	0.026	0.052	0.078	0.104	0.130	0.156	0.182	0.208	0.234	0.260	3.1
200 lb(91 kg)	0.023	0.047	0.070	0.093	0.117	0.140	0.164	0.187	0.210	0.234	3.4
220 lb(100 kg)	0.021	0.042	0.064	0.085	0.106	0.127	0.149	0.170	0.191	0.212	3.8
240 lb(109 kg)	0.019	0.039	0.058	0.078	0.097	0.117	0.136	0.156	0.175	0.195	4.1
260 lb(118 kg)	0.018	0.036	0.054	0.072	0.090	0.108	0.126	0.144	0.162	0.180	4.5

under 0.02% — Below 0.02%0.02%+ — Impairment begins0.05%+ — Over Utah's limit0.08%+ — Over the US legal limit0.15%+ — Severe impairment0.30%+ — Medical emergency

The colour ramp deliberately contains no green. There is no cell in this table that means “safe to drive”. Impairment of judgement, reaction time and divided attention is measurable well below 0.08%, and every figure here is an average that can be badly wrong for an individual.

The law

US legal limits, and what they are not

Every figure below is a per se limit — a level at which the number alone proves the offence, with no further evidence of impairment required. None of them is a safety threshold. Impairment is measurable from the first drink, and a driver can be arrested and convicted below any of these limits if an officer judges them impaired.

Limit	Applies to	Detail
0.08%	Drivers aged 21 and over	The per se limit in 49 states, the District of Columbia, and US territories. Set nationally after the last state adopted it in 2004.
0.05%	Drivers aged 21 and over in Utah	Utah dropped to 0.05% on 30 December 2018, the lowest general limit in the country and the level the National Transportation Safety Board has recommended for every state.
0.04%	Commercial driver's licence holders	Federal rule for anyone operating a commercial motor vehicle, half the ordinary limit. Federal regulation also forbids driving within four hours of consuming any alcohol.
0.00–0.02%	Drivers under 21	Zero-tolerance laws in all 50 states. Most set the threshold at 0.02% or at any detectable amount, so a single drink is an offence.
0.15%	Aggravated or enhanced DUI	Many states add mandatory penalties — longer licence suspension, an ignition interlock, jail time — once a driver measures at or above this level.
Any level	Impaired driving generally	A driver can be arrested and convicted below the per se limit if an officer judges them impaired. Being under a limit is not a defence.

Limits outside the United States are commonly lower — 0.05% across most of Europe, 0.02% in Norway, Sweden and Poland, and zero in a number of countries. Check the local rule wherever you are, and treat every one of them as a floor set by law rather than a level anyone should aim for.

Accuracy

Why Widmark is only an estimate

The equation has four inputs. A real person has dozens of variables, and every one of the factors below moves the answer without appearing anywhere in the formula. This is the reason a calculator can never substitute for a test, and never for a decision to not drive.

food in the stomach

What you ate, and when

A meal slows gastric emptying, so alcohol reaches the small intestine — where nearly all of it is absorbed — more gradually. Eating before drinking can lower the peak substantially. The equation has no term for it.

the absorption phase

Alcohol still on its way in

Widmark assumes every drink is already fully absorbed and evenly distributed. Early in a session that is simply false, so the estimate can read high for someone who has only just started and low for someone still absorbing a recent round.

Absorption usually completes 30–90 minutes after the last drink

lean mass, not weight

Body composition, not the scale

The r factor is a stand-in for total body water. Two people at the same weight with different amounts of lean tissue distribute the same alcohol into different volumes, so their real curves diverge from a shared estimate.

enzyme activity varies

Liver function and genetics

Elimination is driven by alcohol dehydrogenase, and that enzyme's activity varies widely between individuals and between populations. Liver disease, heavy long-term use and inherited enzyme variants all shift it.

Real rates run roughly 0.010–0.025 %/hr against the 0.015 average used here

many drugs interact

Medication and other drugs

Sedatives, opioids, antihistamines, some antibiotics and many other medicines either compound alcohol's effects or alter how fast it clears. Impairment can be severe at a BAC the model calls low.

carbonation speeds it up

Fizz, temperature and mixers

Carbonated and warm drinks tend to move through the stomach faster, raising the peak. A spirit mixed with a fizzy mixer is not absorbed on the same timeline as the same spirit taken neat.

hormonal cycle effects

Hormones and the menstrual cycle

Studies have found alcohol absorption and elimination shifting across the menstrual cycle and with hormonal contraceptives. A single fixed r value cannot represent that.

tolerance hides nothing

Tolerance masks the signal, not the level

A regular drinker may feel and appear less affected at a given BAC, but the concentration in the blood — and the legal exposure, and much of the reaction-time cost — is unchanged. Feeling sober is not evidence.

nobody pours 1.5 oz

The pour you actually had

Free-poured spirits, restaurant wine and craft beer routinely carry well over a standard drink. Miscount what went in the glass and the answer moves by exactly the same proportion, before any biology is even considered.

A 16 fl oz pint at 7% ABV = 1.87 standard drinks, not one

hydration and illness

Hydration, illness and fatigue

Dehydration reduces the water volume alcohol distributes into, nudging concentration up. Illness, fatigue and recent weight change all move the same terms the model treats as fixed.

Myths

What does not sober anyone up

Only time lowers blood alcohol. Everything on this list is folklore that people act on, usually at exactly the moment when acting on it does the most damage.

The claim	What actually happens
Coffee sobers you up	Caffeine is a stimulant, not an antidote. It can make someone feel more alert while their BAC and their impairment are unchanged, which is arguably worse than being visibly drunk.
A cold shower or fresh air helps	Neither touches the blood. Alcohol leaves almost entirely through the liver at a rate you cannot influence by feeling uncomfortable.
Eating afterwards speeds it up	Food only helps before or during drinking, by slowing absorption. Once alcohol is in the bloodstream a meal changes nothing about how fast it clears.
Vomiting clears the alcohol	It may remove what is still in the stomach, but everything already absorbed stays. It also raises the risk of choking, which is what makes leaving someone to sleep it off dangerous.
Beer is safer than spirits	The body responds to grams of ethanol, not to the container. A 16 oz craft pint can carry more alcohol than a measured shot.
You can feel when you are under the limit	Self-assessment is unreliable at exactly the levels where it matters, and alcohol impairs the judgement being used to make the assessment. Feeling fine is not a measurement.

Origin

Where the formula came from

The equation on this page is nearly a century old, which explains both its simplicity and its limits.

Erik Widmark, 1932: The Swedish physician Erik Matteo Prochet Widmark published the distribution model that still carries his name, working from blood samples taken at known times after known doses. His insight was that alcohol distributes into total body water, so concentration can be predicted from dose and a body-water factor.
The r factor: Widmark derived the distribution ratio empirically and reported values clustering around 0.68 for men and 0.55 for women in his own samples. The 0.73 and 0.66 figures used in US driver education and in this calculator come from later work on larger populations and are the values now printed in state handbooks.
The 5.14 constant: The original equation is metric — grams of alcohol over kilograms of body mass. The 5.14 in the US form is purely a unit conversion, folding fluid ounces of ethanol and pounds of body weight into grams per 100 mL of blood.
The 0.015 rate: Widmark called the elimination slope beta. Modern averages put it near 0.015 BAC percentage points an hour for social drinkers, with real values spread roughly between 0.010 and 0.025 depending on enzyme activity, drinking history and liver health.
Why it survives: Nothing better exists that needs only four inputs a person can supply from memory. Forensic toxicologists still use Widmark for back-extrapolation in court, but with error bounds, case-specific r values, and a great deal of care that a web calculator cannot reproduce.

Worth knowing

Rules worth remembering

Six things that decide whether an estimate is anywhere near reality, none of which the equation asks you for.

count drinks, not glasses

The input is the biggest error

Every other source of error is biological and hard to fix. This one is arithmetic, and it is where most people go wrong before the formula even runs.

One 16 fl oz craft pint at 7% = 1.87 standard drinks

H runs from the first drink

Time is counted from the start

Metabolism begins as soon as alcohol reaches the blood, so the clock starts with the first drink. Counting from the last one overstates the estimate substantially on a long session.

0.094% peak − 0.030% over 2 hr = 0.064%

only time lowers it

Nothing accelerates clearance

Coffee, cold air, a shower, food afterwards, exercise, sleep — none of them change the rate the liver works at. They change how a person feels, which is worse than useless when the feeling is used as evidence.

tolerance ≠ lower BAC

Feeling fine proves nothing

A regular drinker may show fewer outward signs at the same concentration. The blood alcohol, the legal exposure, and much of the reaction-time cost are unchanged. Self assessment is least reliable exactly where it matters most.

drink for drink, lighter is higher

Body size drives the answer

The same alcohol diluted into less body water reaches a higher concentration. It is the single largest term in the equation after the amount you drank.

4 drinks · 180 lb male → 0.094% peak · 2 drinks · 140 lb female → 0.067% peak

an estimate, never a permission

What the number is for

Understanding, curiosity, and a sense of scale — how much a pour really is, how slowly alcohol leaves, how far below a legal limit impairment starts. Not for deciding whether to drive. That decision has one safe answer.

In context

Where the model crosses the lines

People search for the drink count that crosses 0.08%, so here it is stated plainly — and stated with what it actually means. These are points where an equation crosses a legal line, computed at hour zero before any metabolism. They are not allowances, and the distance between them and the level where impairment begins is small.

0.08% · 180 lb · r 0.73

A larger male body

And crosses the level at which divided attention and visual tracking measurably degrade long before that. The gap between the first drink and the legal line is a couple of servings, not an evening.

crosses 0.08% at about 3.4 standard drinks

0.08% · 140 lb · r 0.66

A lighter female body

Same alcohol, less body water, higher concentration. This is why a shared round produces very different numbers around one table, and why matching someone drink for drink tells you nothing.

crosses 0.08% at about 2.4 standard drinks

Read those two figures as a warning about how quickly the line arrives, not as a target to approach. Neither is a statement that fewer drinks make driving acceptable — the safe amount before driving is none, at any body weight.

FAQ

Common questions

Use the Widmark equation: BAC% = (A × 5.14 / (W × r)) − 0.015 × H. A is the alcohol you drank in fluid ounces of pure ethanol — 0.6 fl oz for each US standard drink — W is your body weight in pounds, r is the distribution ratio (0.73 for men, 0.66 for women), and H is the hours since your first drink. For a 180 lb man who has had four standard drinks over two hours, A is 2.4 fl oz, so the peak is 2.4 × 5.14 ÷ (180 × 0.73) = 0.094%, and subtracting 0.015 × 2 leaves an estimate of about 0.064%. It is an estimate from a population average, not a measurement, and it must never be used to decide whether to drive.

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