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Blood alcohol calculator - estimate your BAC and sober-up time

Enter your sex, body weight, the drinks you had and when you started - the calculator estimates your blood alcohol level (per mille and % BAC) and when it should fall below common legal limits.

  • Free
  • No sign-up
  • Private
  • Runs locally
This result is only a rough estimate.Never use it to decide whether you are fit to drive. Your real blood alcohol level depends on food, medication, liver health, hydration and many other factors, and may be higher than calculated. If you have been drinking, do not drive. Only a calibrated breathalyser or a blood test gives a reliable reading.
kg
h

E.g. 1.5 = an hour and a half ago.

‰/h

Usually 0.10-0.15‰ per hour. A lower value gives a more cautious result.

Drinks

  • Beer
    ml
    %
Estimated level now
0.55‰
about 0.055% BAC (g per 100 ml)
Peak level (theoretical)
0.70‰
Pure alcohol
39.5 g
Below 0.5‰
in 0 h 22 min
Below 0.2‰
in 2 h 22 min
Fully sober (0.0‰)
in 3 h 42 min

Calculated with the Widmark formula: it assumes all alcohol is absorbed at once and eliminated at a constant rate. In reality your level may keep rising for 0.5-2 hours after your last drink.

Results are for information only and are not legal, tax or financial advice.

How to estimate your blood alcohol level

  1. 1.

    Enter sex and body weight

    Sex sets the Widmark factor (0.7 for men, 0.6 for women); body weight determines how much body water the alcohol is spread through.

  2. 2.

    Add your drinks

    Pick beer, wine, spirits or a custom drink and set the number of servings. You can change the volume and ABV.

  3. 3.

    Enter the time since you started

    Your body has been eliminating alcohol since then - 0.15‰ per hour by default.

  4. 4.

    Read the estimate

    See your estimated level now and when it should drop below 0.5‰, 0.2‰ and to zero. It is an estimate only - never use it to decide whether to drive.

The Widmark formula

Blood alcohol is estimated with the Widmark formula: BAC [‰] = A / (r × W) − β × t, where A is grams of pure alcohol, r the Widmark factor (about 0.7 for men and 0.6 for women), W body weight in kg, β the elimination rate (0.10-0.15‰ per hour) and t the hours since you started drinking.

Grams of alcohol = volume [ml] × ABV [%] / 100 × 0.789 (the density of ethanol). A 500 ml beer at 5% contains 19.7 g, a 150 ml glass of 12% wine 14.2 g and a 50 ml shot of 40% spirits 15.8 g.

Example: a man weighing 80 kg drinks four 500 ml beers (78.9 g). Peak level: 78.9 / (0.7 × 80) = 1.41‰ (0.141% BAC). Two hours after he started: 1.41 − 2 × 0.15 = 1.11‰. He would need about another 4 h 4 min to get below 0.5‰ and 7 h 24 min to reach zero.

Per mille, % BAC and legal limits

1‰ (one per mille) means 1 gram of alcohol per litre of blood, which equals 0.1% BAC (g per 100 ml). So 0.5‰ = 0.05% BAC and 0.8‰ = 0.08% BAC.

LimitWhere it typically applies
0.0-0.2‰ (0.00-0.02%)Zero-tolerance countries, novice and professional drivers in many countries
0.5‰ (0.05%)Most of Europe, Australia
0.8‰ (0.08%)Most US states, Canada (criminal limit), England and Wales

Limits and penalties differ between countries and change over time - always check your local law. The only safe rule is not to drive after drinking any alcohol.

How fast does alcohol leave your body?

The liver removes roughly 0.10-0.15‰ per hour, which is about 7-10 g of pure alcohol - half a beer. Coffee, cold showers, sleep and hangover pills do not speed this up.

At 0.15‰ per hour it takes about 10 hours to get from 1.5‰ to zero; at 0.10‰ per hour it takes 15 hours. Set a lower rate in the calculator if you want a more cautious result. This is why many drivers are still over the limit the morning after a party.

Why the result is only a rough guide

The Widmark formula assumes all alcohol is absorbed instantly and eliminated at a constant rate. In reality, your level keeps rising for 30 minutes to 2 hours after your last drink - more slowly after a large meal, faster on an empty stomach.

Body composition, medication, liver disease, fatigue, age and dehydration all change the result, and differences between people can reach tens of percent. This calculator does not replace a breathalyser or blood test and must never be used to decide whether you can drive.

Frequently asked questions

What is my BAC after one beer?

+
A 500 ml beer at 5% gives a man weighing 80 kg a peak of about 0.35‰ (0.035% BAC) and a woman weighing 60 kg about 0.55‰ (0.055%). The body removes about 0.10-0.15‰ per hour.

How long until I am sober?

+
Divide your peak level by the elimination rate: at 0.15‰ per hour, 1.2‰ takes about 8 hours to reach zero. Individual rates vary, so treat any estimate as a minimum.

What is the difference between ‰ and % BAC?

+
‰ is grams of alcohol per litre of blood, % BAC is grams per 100 ml. Divide per mille by 10 to get % BAC: 0.8‰ = 0.08%.

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

+
Women usually have less body water, so the Widmark factor is about 0.6 instead of 0.7. At the same weight and alcohol intake, a woman’s level is roughly 17% higher.

Does coffee or sleep sober you up faster?

+
No. The liver breaks alcohol down at a fairly constant rate. Coffee may make you feel more alert, but your blood alcohol level stays the same.

Is this calculator accurate?

+
No - it gives a rough estimate. It ignores food, medication, health and absorption speed, and your real level may be higher. Never use it to decide whether to drive.

Updated: