calcs.vodka /us/
State Utah is the one state with a lower 0.05% limit; every other state uses 0.08%.
United StatesTier 3

BAC calculator

Weight, sex, standard drinks and time elapsed in. An estimated blood alcohol content out, checked against your state's legal limit.

Free·No sign-up·Last checked 2026-08-27
lb
Sex
Sets the Widmark distribution ratio, r
0.6 fl oz / 14 g ethanol each — see the standard drink calculator
hr
Estimated BAC
0.098% BAC
Over the 0.08% limit
0.00%0.08% limit0.20%
Under 21: 0.00–0.02% (under 21, zero-tolerance)
Commercial (CDL): 0.04% (CDL, federal FMCSA)
Hours until 0.00%
6.5hr
Hours until under the limit
1.2hr
Estimate only
Estimate only. Many factors affect BAC. Do not use to decide whether to drive. Not legal or medical advice.
Formula — Widmark
Alcohol (g) = standard drinks × 14 BAC% = (alcohol_g ÷ (weight_g × r)) × 100 − (0.015 × hours) weight_g = weight_lb × 453.592. r = 0.68 (male) or 0.55 (female).
Worked example. 160 lb male, 4 drinks, 1 hour → 56 g alcohol ÷ (72,575 g × 0.68) × 100 − 0.015 = 0.098%.
Method
Widmark formula, population-average distribution ratio
r (male)
0.68
r (female)
0.55
Elimination rate
0.015% BAC per hour
These are the values from Widmark's original research. Several other published calculators use 0.73/0.66 instead — a real disagreement in the literature, not a typo. Either constant set gives an estimate, not a measurement.
Sources
  1. 01NHTSA — Drunk driving
  2. 02NHTSA — Zero-tolerance and lower-BAC laws
  3. 03FMCSA — Commercial driver 0.04% rule — 49 CFR §382/§383
  4. 04NIAAA — What is a standard drink

Questions

It's a population-average model. Food in the stomach, medications, individual metabolism, drink strength errors and the exact timing of drinks can all shift real BAC well away from the estimate in either direction.
Several r constants exist in the literature. This calculator uses 0.68 for men and 0.55 for women, values used by the original Widmark research; some other calculators publish 0.73/0.66 from a different source. The difference changes the estimate by several tenths of a percent, one reason to treat any single number as approximate.
Food slows how fast alcohol is absorbed, which can lower the peak BAC and spread it over more time, but it does not change the total amount of alcohol your body has to process.
No. It gives an estimate for reference only. The only reliable way to know your BAC is a breath or blood test, and the only way to guarantee you're under any limit is not to drive after drinking.