Is this accurate enough to decide if I can drive?

No. The Widmark model ignores food, drink timing, medications, and individual metabolism, so your true BAC can be much higher or lower. Never rely on any calculator to judge fitness to drive — if you have been drinking, do not drive.

What does the 0.08 threshold mean?

In most U.S. states a BAC of 0.08 or above is the legal limit for driving. This tool labels 0.08 to 0.15 as "legally impaired," but legal limits and penalties vary by jurisdiction and are lower for commercial and underage drivers.

How fast does alcohol leave the body?

On average the body eliminates alcohol at roughly 0.015 BAC per hour, and that rate cannot be sped up by coffee, water, or a cold shower. The "time to sober" figure here simply divides your BAC by 0.015.

Why does sex change the result?

Body water content differs on average between sexes, so alcohol distributes differently. The formula uses a distribution constant of 0.73 for men and 0.66 for women, which raises the estimated BAC for women at the same weight and intake.

BAC Calculator

Number of Drinks2

Drink Type

Weight

lbs

Gender

Hours Since First Drink0 hrs

Blood Alcohol Content0.047

Time to Sober3.1 hours

Impairment LevelRelaxed

Blood alcohol concentration (BAC) estimates the percentage of alcohol in your bloodstream after drinking. This calculator uses a Widmark-style model that accounts for the drink type and its alcohol content, your body weight, your sex, and the time elapsed since you started drinking, subtracting alcohol your liver has already metabolised. Results are rough estimates and must never be used to decide whether it is safe to drive.

Formula

BAC = (oz_alcohol × 5.14) / (weight_lb × r) − 0.015 × hours

oz_alcohol: Total pure alcohol consumed in ounces (drinks × drink oz × ABV)
weight_lb: Body weight in pounds
r: Sex distribution constant: 0.73 male, 0.66 female
hours: Hours since drinking began; alcohol clears at ~0.015 BAC per hour

How it works

Choose a drink type — beer (12 oz, 5% ABV), wine (5 oz, 12%), shot (1.5 oz, 40%), or cocktail (4 oz, 15%) — and enter the number of drinks, your weight in pounds, your sex, and the hours since you began.
The tool computes ounces of pure alcohol per drink, multiplies by the number of drinks, and applies the Widmark formula with a sex distribution constant (0.73 for men, 0.66 for women).
It subtracts 0.015 per hour for metabolism, reports your estimated BAC, an impairment label, and the hours until BAC returns to zero at that elimination rate.

Worked example

A 180 lb man has 4 beers over 2 hours.

Alcohol per beer: 12 oz × 0.05 = 0.6 oz; total = 4 × 0.6 = 2.4 oz.
Raw BAC = (2.4 × 5.14) / (180 × 0.73) = 12.336 / 131.4 = 0.0939.
Subtract metabolism: 0.0939 − 0.015 × 2 = 0.0639.

BAC ≈ 0.064 → "Reduced coordination"; about 4.3 hours to reach 0.

Frequently asked questions

Is this accurate enough to decide if I can drive?: No. The Widmark model ignores food, drink timing, medications, and individual metabolism, so your true BAC can be much higher or lower. Never rely on any calculator to judge fitness to drive — if you have been drinking, do not drive.
What does the 0.08 threshold mean?: In most U.S. states a BAC of 0.08 or above is the legal limit for driving. This tool labels 0.08 to 0.15 as "legally impaired," but legal limits and penalties vary by jurisdiction and are lower for commercial and underage drivers.
How fast does alcohol leave the body?: On average the body eliminates alcohol at roughly 0.015 BAC per hour, and that rate cannot be sped up by coffee, water, or a cold shower. The "time to sober" figure here simply divides your BAC by 0.015.
Why does sex change the result?: Body water content differs on average between sexes, so alcohol distributes differently. The formula uses a distribution constant of 0.73 for men and 0.66 for women, which raises the estimated BAC for women at the same weight and intake.

Related calculators

BMR Calculator Calorie Calculator Body Fat Calculator