BAC Calculator

Estimate your Blood Alcohol Content (BAC) from the number of drinks, your body weight, and the time since your first drink. Includes an estimated time until you return to sober.

For informational use only. This is a rough estimate and must never be used to decide whether it is safe to drive or operate machinery. Many factors affect real BAC. When in doubt, do not drive.

Metric (kg) Imperial (lb)

Biological Sex:

Body water distribution differs, affecting the estimate.

Weight (kg):

Standard Drinks:

1 standard drink ≈ 14 g of pure alcohol (12 oz beer, 5 oz wine, or 1.5 oz spirits).

Hours Since First Drink:

How It Works

This calculator uses the Widmark formula, a widely used method for estimating blood alcohol content from the amount of alcohol consumed and body characteristics.

Widmark Formula

BAC (%) = (A / (r × W)) × 100 − (β × t)

A = grams of pure alcohol consumed (drinks × 14 g)
W = body weight in grams
r = Widmark distribution ratio (0.68 male, 0.55 female)
β = elimination rate ≈ 0.015 % per hour
t = hours since the first drink

Estimated Effects by BAC Level

0.02%: Slight relaxation, mild mood changes.
0.05%: Lowered alertness, impaired judgment.
0.08%: Legal driving limit in many regions; impaired coordination.
0.15%: Significant impairment of balance and reaction.
0.30%+: Severe impairment, risk of alcohol poisoning.

Sober-Time Estimate

The body eliminates alcohol at roughly a constant rate (about 0.015% BAC per hour). The sober-time estimate divides your current BAC by this rate. Actual times vary between individuals.

Safety Disclaimer: BAC estimates are not a measure of your actual impairment or legal fitness to drive. Food, medication, health, drinking pace, tolerance, and metabolism all change real results. Never drink and drive. If you have been drinking, arrange a taxi, rideshare, or designated driver.

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