CanadaTier 3
BAC calculator
Weight, sex, standard drinks and time elapsed in. An estimated blood alcohol content out, checked against Canada's warn range and criminal "over 80" limit.
Free·No sign-up·Last checked 2026-08-27
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 × 13.6
BAC% = (alcohol_g ÷ (weight_g × r)) × 100 − (0.015 × hours)
weight_g = weight_kg × 1000. r = 0.68 (male) or 0.55 (female).
Worked example. 72 kg male, 4 drinks, 1 hour → 54.4 g alcohol ÷ (72,000 g × 0.68) × 100 − 0.015 = 0.096%.
Method
Widmark formula, population-average distribution ratio, Canada's two-tier zone system
- r (male)
- 0.68
- r (female)
- 0.55
- Elimination rate
- 0.015% BAC per hour
- Warn range
- 0.05–0.079%
- Criminal ("over 80")
- 0.08%+
Canada uses two thresholds, not one. 0.05–0.079% BAC is the "warn range" — provinces can issue an immediate roadside administrative licence suspension, which is separate from and does not require a criminal charge. 0.08% and above is the Criminal Code s.320.14 "over 80" offence. The Widmark r values here (0.68 male, 0.55 female) are the values from the original research; some 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
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.
0.05–0.079% BAC falls in the warn range, where provinces can issue an immediate roadside administrative licence suspension — separate from and short of a criminal charge. 0.08% and above is the Criminal Code "over 80" offence. Novice (G1/G2) and commercial drivers face a 0.00% zero-tolerance limit instead of either threshold.
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.