BAC Calculator 2026: Widmark Estimate vs Legal Limits
Weight, sex, drinks and elapsed time feed the Widmark formula, then the estimate meets the legal ceiling: 0.05% in much of Europe, 0.08% in the UK.
Disclaimer: This is an estimate only. Actual BAC varies with food, metabolism, medication and other factors. Never drive if you have consumed alcohol. When in doubt, don't drive.
Your Details
Drinks Consumed
BAC Level
Enter your details above to calculate.
Legal BAC Limits by Country
Your estimated BAC compared to legal driving limits. Red = over limit.
| Country | BAC Limit | Your BAC | Status |
|---|
This calculator uses the Widmark formula with a metabolism rate of 0.015% per hour. Results are estimates only. Individual results may vary significantly. Never drive after consuming alcohol.
The Widmark formula does the arithmetic guesswork gets wrong: grams of pure alcohol against body water — 0.68 for men, 0.55 for women — minus the roughly 0.015% your body clears each hour. Choose a country and the tool sets that estimate against its legal ceiling — 0.05% across much of Europe, 0.08% in the UK and the US, 0.00% where tolerance is zero — and against the time left until you reach 0.00%. It remains an estimate, not a defence — enforcement measures the driver, never the formula.
Blood Alcohol Content Calculator
Estimate your blood alcohol concentration (BAC) based on your weight, gender, number of drinks, and time elapsed since your first drink. This tool uses the Widmark formula, the internationally accepted scientific method for BAC estimation.
What This Tool Does
Enter your details and the calculator estimates your current BAC level, then compares it against the legal driving limit for any country you select. The result shows whether you are likely above or below the legal limit and how long until your BAC reaches zero.
How to Use It
- Select your gender and enter your body weight.
- Add each drink you have consumed, specifying the type (beer, wine, spirits) and volume.
- Enter how many hours have passed since your first drink.
- Select the country whose legal limit you want to compare against.
- Review your estimated BAC and the time until you reach 0.00%.
Worked Example: 3 beers, 75 kg, over 2 hours
A 75 kg man who drinks three 500 ml beers (5%) over 2 hours reaches an estimated BAC of about 0.09% — over the 0.05% limit used across most of Europe, and over the 0.08% UK/US limit too. He would not be safely below 0.05% for roughly 5–6 more hours (about 7.8 hours from his first drink).
Here is the calculation the tool runs, using the Widmark formula:
- Alcohol consumed: 3 × 20 g = 60 g (a 500 ml, 5% beer ≈ 20 g of pure alcohol)
- Widmark formula: BAC = (A ÷ (r × W)) − (β × t)
- A = 60 g alcohol · r = 0.68 (male body-water constant; 0.55 for women) · W = 75,000 g · β = 0.015%/hour · t = 2 hours
- Result: (60 ÷ (0.68 × 75,000)) × 100 − (0.015 × 2) = 0.118% − 0.03% = ≈ 0.09% BAC
| Input | Value |
|---|---|
| Body weight | 75 kg (male) |
| Drinks | 3 × 500 ml beer (5%) = 60 g alcohol |
| Time since first drink | 2 hours |
| Estimated BAC | ≈ 0.09% |
| Verdict | Over the limit in France, Germany, Spain, Italy (0.05%) and the UK/US (0.08%) |
| Time to reach 0.00% | ≈ 7.8 hours from the first drink |
Change any input in the calculator above to see your own number and the exact country limits it crosses.
Important Limitations
This calculator provides an estimate only. Actual BAC varies based on food intake, metabolism, medication, hydration, and individual physiology. Never rely solely on any calculator to decide whether it is safe to drive. When in doubt, do not drive.
Data Sources
BAC limits for each country are sourced from official government transport authorities, the World Health Organization Global Status Report on Road Safety, and the European Transport Safety Council. The Widmark formula parameters follow the standard constants established in forensic toxicology literature.