Blood Alcohol Calculator (Widmark Formula Estimate)
A rough estimate of blood alcohol concentration after a number of drinks, from your weight and sex, and how long until it reaches zero.
Results
What this tool does
Erik Widmark's 1932 formula treats the body as a container of water: alcohol in grams divided by body weight times a distribution factor r, about 0.68 for men and 0.55 for women because women carry proportionally less body water. The body then clears roughly 0.015 g per 100 mL an hour, though anywhere from 0.010 to 0.020 occurs, and nothing speeds it up — not coffee, not a cold shower. The result is a rough estimate at best: food in the stomach, how fast you drink, medication and your own build can shift the real value a lot, and legal limits differ by country. Never use it to decide whether you are fit to drive.
Formula
peak BAC (g/100 mL) = alcohol (g) ÷ (r × weight (kg) × 10) · BAC now = peak − β × hours (Widmark: r = 0.68 men, 0.55 women; β ≈ 0.015 per hour)
Variables
| Symbol | Meaning | Unit |
|---|---|---|
n | Number of drinks | — |
gd | Pure alcohol in one drink (US standard drink 14 g, UK unit 8 g) | g |
kg | Body weight | kg |
sx | Sex | — |
t | Hours since the first drink | h |
be | Elimination rate (about 0.015 % an hour; 0.010–0.020) | %/h |
BC | Estimated blood alcohol now (g per 100 mL) | g/100 mL |
PM | The same in grams per litre (per mille) | g/L |
PK | Highest it could reach if all were absorbed (g per 100 mL) | g/100 mL |
HZ | Hours from now until it reaches zero | h |
Worked example
- Number of drinks3
- Pure alcohol in one drink (US standard drink 14 g, UK unit 8 g)14 g
- Body weight75 kg
- Sex1
- Hours since the first drink2 h
- Elimination rate (about 0.015 % an hour; 0.010–0.020)0.015 %/h
- Estimated blood alcohol now (g per 100 mL)0.052 g/100 mL
- The same in grams per litre (per mille)0.52 g/L
- Highest it could reach if all were absorbed (g per 100 mL)0.082 g/100 mL
- Hours from now until it reaches zero3.5 h
Limitations
- This tool is informational only. It does not diagnose, treat or replace a qualified health professional. Speak to a doctor before making decisions about your health.
- The result is an estimate based only on the values you type. Real situations often include factors this calculator does not know about.