BAC Calculator: Estimate Blood Alcohol Content and Time to Sober Up

BAC calculator

Estimate your blood alcohol content from drinks, drink size, strength, weight, sex and hours since you started. See how you compare to driving limits and how long until you are sober.

This is not medical advice

Estimate only. Not medical advice. Check with a doctor or pharmacist before acting on it. Read the full note

These calculators use published population formulas. They do not know your medical history and cannot diagnose, treat or replace a doctor, pharmacist or dietitian. Do not change medication, dosing, eating or drinking decisions on the basis of a number here. If you are pregnant, under 18, over 65, have a health condition or take medication, ask a clinician first. In an emergency call your local emergency number.

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Compared to driving limits

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Where	Limit	You

Time to sober up

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Blood alcohol over time, hour by hour

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Time	BAC	Likely effects

BAC chart for men by weight and drinks

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Weight	1 drink	2	3	4	5	6
100 lb (45 kg)	0.045	0.091	0.136	0.182	0.227	0.272
120 lb (54 kg)	0.038	0.076	0.113	0.151	0.189	0.227
140 lb (64 kg)	0.032	0.065	0.097	0.130	0.162	0.195
160 lb (73 kg)	0.028	0.057	0.085	0.113	0.142	0.170
180 lb (82 kg)	0.025	0.050	0.076	0.101	0.126	0.151
200 lb (91 kg)	0.023	0.045	0.068	0.091	0.113	0.136
220 lb (100 kg)	0.021	0.041	0.062	0.083	0.103	0.124
240 lb (109 kg)	0.019	0.038	0.057	0.076	0.095	0.113

Peak BAC in percent right after drinking, US standard drinks of 14 g alcohol (a 12 oz beer at 5%, a 5 oz glass of 12% wine or 1.5 oz of 40% spirits). Subtract 0.015 for every hour since the first drink. Estimates only: never use them to decide whether to drive.

BAC chart for women by weight and drinks

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Weight	1 drink	2	3	4	5	6
100 lb (45 kg)	0.056	0.112	0.168	0.224	0.281	0.337
120 lb (54 kg)	0.047	0.094	0.140	0.187	0.234	0.281
140 lb (64 kg)	0.040	0.080	0.120	0.160	0.200	0.241
160 lb (73 kg)	0.035	0.070	0.105	0.140	0.175	0.210
180 lb (82 kg)	0.031	0.062	0.094	0.125	0.156	0.187
200 lb (91 kg)	0.028	0.056	0.084	0.112	0.140	0.168
220 lb (100 kg)	0.026	0.051	0.077	0.102	0.128	0.153
240 lb (109 kg)	0.023	0.047	0.070	0.094	0.117	0.140

Peak BAC in percent right after drinking, US standard drinks of 14 g alcohol. Subtract 0.015 for every hour since the first drink. Estimates only: never use them to decide whether to drive.

You can enter what you drank either as a number of drinks of a given size, or as one total amount at one strength, for example 700 ml of 12% wine or 1.5 liters of 5% beer. Both are turned into grams of pure alcohol (volume × strength × 0.789), which is what the formula uses.

Blood alcohol content (BAC) is the share of alcohol in your blood by weight: 0.08% means 8 grams of alcohol per 10 liters of blood. This calculator estimates it with the Widmark formula used in forensic science, then shows how you compare to driving limits and how long until you are back to zero.

How it is calculated

Alcohol consumed in grams = number of drinks × drink size × strength × 0.789 (the density of ethanol). A 355 ml beer at 5% holds about 14 g, which is one US standard drink.
Peak BAC = grams of alcohol ÷ (body weight in kg × r × 10). The factor r is the share of body weight that is water where alcohol spreads: about 0.68 for men and 0.55 for women, which is why the same drinks give women a higher BAC.
Your body clears alcohol at a nearly constant 0.015% per hour. Current BAC = peak − 0.015 × hours since the first drink.

Example

A 75 kg man has three 355 ml beers at 5% over two hours: 3 × 14 g = 42 g of alcohol. Peak BAC = 42 ÷ (75 × 0.68 × 10) = 0.082%. After two hours: 0.082 − 0.030 = 0.052%. Under the US limit, over the limit in most of Europe, and about 3.5 hours from zero.

Why the real number can be higher or lower

Widmark assumes alcohol is absorbed instantly and evenly. Drinking on an empty stomach pushes the peak higher and earlier; a large meal spreads it out. Body composition matters: more muscle means more water and a lower BAC for the same weight. The formula is typically within about 20% of a breath test, which is good enough for planning and useless for deciding whether you are safe to drive.

What does not sober you up

Coffee, cold showers, food after the fact, exercise and sleep do not speed up clearance. The liver processes about one standard drink per hour and cannot be hurried. If you had five drinks, you need roughly five hours from the last one.

Frequently asked questions

How many drinks does it take to reach 0.08?

Roughly four drinks in two hours for a 75 kg man, or three for a 60 kg woman. It depends on weight, sex, drink strength and food, which is why the calculator asks for all of them.

How long does it take for alcohol to leave your system?

About one standard drink per hour, or 0.015% BAC per hour. From 0.08% you need at least five to six hours to reach zero. Breath and blood tests detect alcohol for that long; urine and hair tests for much longer.

Is the BAC calculator accurate enough to decide if I can drive?

No. It is an estimate with a margin of roughly 20%, and a breath test at the roadside will not care about your calculation. If you have been drinking, do not drive.

Why do women get a higher BAC from the same drinks?

Alcohol spreads through body water, and women have a lower proportion of water to body weight on average. The Widmark factor accounts for this: 0.55 versus 0.68 for men.

What is a standard drink?

In the US, 14 g of pure alcohol: a 355 ml beer at 5%, 150 ml of wine at 12%, or 44 ml of spirits at 40%. The UK uses units of 8 g, so a US standard drink is 1.75 UK units.

Sources

By Calcelate Team. Formula from the sources above.

2026-09-14 · Formula and texts checked
2026-09-14 · Emergency numbers verified against official sources