Blood Alcohol Calculator
Estimate blood alcohol concentration from your weight, sex, number of drinks and hours elapsed.
Last updated · View algorithm, constants and default inputs (JSON)
About this calculator
This is a rough educational estimate using a simplified Widmark model and fixed assumptions. Actual BAC varies widely. Do not use it to decide whether it is safe or legal to drive; any alcohol can impair driving. The 14 g per drink is the U.S. standard drink amount.
Worked example
calculated with the default values below
Sex Male · Body weight 75 kg · U.S. standard drinks (14 g each) 2 drinks · Hours since first drink 2 h Estimated BAC 0.025 % · Alcohol consumed 28.0 g · Estimated hours remaining at this model rate 1.7 h
General background references
Disclaimer
These calculators are for general information only and are not a medical device, a diagnosis or a treatment plan. Reference ranges describe populations, not individuals, and do not account for pregnancy, medication, disability or athletic training. Discuss your own situation with a qualified healthcare professional.
Implementation source
This record describes the implementation used by this page. It is not independent validation. External references, when available, support only the stated formula or definition; estimates and custom rules retain their own assumptions.
Formula and variables
BAC = max(100·14n/(1000·W·r) − 0.015t, 0)
- n
- Standard drinks (14 g alcohol each)
- W
- Body weight (kg)
- r
- Widmark factor (0.55 female, 0.68 male)
- t
- Hours since drinking
- BAC
- Blood alcohol content (%)
Estimate only; the body eliminates roughly 0.015% per hour; time to sober = peak ÷ 0.015; weight is converted from kilograms to grams.
Frequently asked questions
How does the body-water factor affect this BAC estimate?
The estimate subtracts 0.015 BAC percentage points per elapsed hour, floors the current modeled BAC at zero, then divides that current estimate by 0.015 for the remaining-time figure. It uses fixed assumptions and cannot determine actual BAC or whether driving is safe or legal. Any alcohol can impair driving.