Estimate your blood alcohol concentration — and why not to drive.
The Widmark formula divides the alcohol you drank by your body weight and a sex-based factor, then subtracts about 0.015% per hour. A 75 kg man who has three US-sized drinks and waits an hour has an estimated BAC near 0.067%. Never drink and drive.
Blood alcohol concentration (BAC) is the amount of alcohol in your blood. This calculator estimates it with the Widmark formula from your weight, sex, number of drinks, the alcohol in each drink and the hours since you started. It also shows roughly when your BAC would reach zero, and what different BAC levels do to the body.
This is a rough estimate and must never be used to judge whether you are safe to drive. Actual BAC depends on food, hydration, medicines, health and how fast you drank, and can be much higher than shown. India's limit for drivers is 30 mg per 100 ml of blood (0.03%), and many countries allow 0.05–0.08% or less. If you drink, arrange a driver, taxi or public transport. For health measures see the BMI Calculator and Calories Burned Calculator.
The calculator applies the standard published formulas step by step.
| Item | Value |
|---|---|
| Alcohol consumed | 42 g |
| Estimated peak BAC (no elimination) | 0.082% |
| Estimated BAC after 1 h (0.015% eliminated per hour) | 0.067% |
| In mg per 100 ml of blood | 67 mg |
| Roughly sober (BAC 0) in | 4.5 hours |
| BAC | Typical effects |
|---|---|
| 0.02–0.03% | Slight mood change, slightly slower reactions |
| 0.05% | Reduced coordination and alertness |
| 0.08% | Legal driving limit in the US, England and Wales |
| 0.10–0.15% | Clear impairment of balance, speech and judgement |
| 0.20% | Confusion, nausea, blackouts |
| 0.30% | Stupor — risk of passing out |
| 0.40%+ | Life-threatening |
| Drinks | Estimated BAC |
|---|---|
| 1 drink | 0.012% |
| 2 drinks | 0.04% |
| 3 drinks | 0.067% |
| 5 drinks | 0.122% |
| 8 drinks | 0.205% |
With the Widmark formula, which divides the alcohol consumed by body weight and a body-water factor, then subtracts the alcohol your body eliminates over time.
30 mg of alcohol per 100 ml of blood (0.03%) under the Motor Vehicles Act. Other countries have different limits, many at 0.05–0.08%.
The body clears about 0.015% BAC per hour, so one drink takes roughly 1–2 hours. Coffee, cold showers and food do not speed it up.
Food, hydration, medicines, health, genetics and drinking speed all change BAC, and drink strengths vary widely.
No. Never use any calculator to decide whether to drive after drinking. Do not drive if you have had any alcohol.
If someone is unconscious, cannot be woken, is vomiting repeatedly, has slow or irregular breathing or cold, blue-tinged skin after drinking, call emergency services immediately.
It uses the published formula: BAC (%) = alcohol (g) ÷ (weight (g) × r) × 100 − 0.015 × hours The full method and a worked example are shown on this page.
No. The calculator gives general estimates for information and education. It cannot diagnose or treat anything, so please speak to a doctor or qualified professional about your own health.
Yes. Choose centimetres or feet and inches for height, and kilograms, pounds or stone for weight; the results are converted for you.
No. Everything is calculated in your browser and nothing you enter is uploaded or saved.
