calcs.vodka /au/
Licence type Learner and provisional (P1/P2) drivers must record zero — 0.00 g/100mL; full licence holders have a 0.05 limit.
AustraliaTier 3

BAC calculator

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

Free·No sign-up·Last checked 2026-08-27
kg
Sex
Sets the Widmark distribution ratio, r
10 g ethanol each — see the standard drink calculator
hr
Estimated BAC
0.063g/100mL
Over the 0.05 limit
0.000.05 limit0.20
Learner/provisional: 0.00 (learner and provisional P1/P2)
Heavy/passenger/dangerous goods: 0.00–0.02
Hours until 0.00
4.2hr
Hours until under the limit
0.9hr
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 × 10 BAC (g/100mL) = (alcohol_g ÷ (weight_g × r)) × 100 − (0.015 × hours) weight_g = weight_kg × 1000. r = 0.68 (male) or 0.55 (female).
Worked example. 75 kg male, 4 drinks, 1 hour → 40 g alcohol ÷ (75,000 g × 0.68) × 100 − 0.015 = 0.063 g/100mL.
Method
Widmark formula, population-average distribution ratio
r (male)
0.68
r (female)
0.55
Elimination rate
0.015 g/100mL 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. 01Department of Health — Alcohol and driving
  2. 02NSW — Drink driving and BAC limits
  3. 03VicRoads — Drink driving

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 gram per 100 mL, 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.
Zero-tolerance (0.00) rules apply to learner and provisional (P1/P2) licence holders in every state, removing any margin while newer drivers build experience. Full licence holders have a 0.05 limit instead. Check your state's road authority for exact conditions.