About the BAC Calculator
A blood alcohol content calculator estimates the concentration of alcohol in your bloodstream from the number of drinks, your body weight, sex, and time elapsed. It is an educational estimate only — actual BAC varies substantially between individuals and cannot be predicted reliably.
The formula
Widmark: BAC = (alcohol g / (weight g · r)) · 100 − (0.015 · hours)r is the Widmark factor, roughly 0.68 for men and 0.55 for women, reflecting differences in body water distribution. Alcohol is eliminated at approximately 0.015 percent BAC per hour.
How to use this calculator
- 1Enter your Number of Drinks (12oz beer / 5oz wine / 1.5oz spirit). The field starts at
3, which you can overwrite. - 2Enter your Body Weight (kg). The field starts at
75, which you can overwrite. - 3Enter your Gender (1=Male, 0=Female). The field starts at
1, which you can overwrite. - 4Enter your Hours Drinking. The field starts at
2, which you can overwrite. - 5Read the result straight away — it recalculates as you type, so there is no button to press. Use Share to copy a link that reopens the page with your exact numbers filled in.
Worked example
| Input | Value |
|---|---|
| Number of Drinks (12oz beer / 5oz wine / 1.5oz spirit) | 3 |
| Body Weight (kg) | 75 |
| Gender (1=Male, 0=Female) | 1 |
| Hours Drinking | 2 |
Result
Estimated BAC: 0.047%
Status: Mild euphoria
Hours to Sober: ~3.1 hrs
⚠ Never drink and drive. Legal limit is typically 0.08%.
Those are the values the page loads with, so you can reproduce this result yourself and then change one field at a time to see what drives the outcome.
Understanding your result
Elimination is essentially linear and slow — about one standard drink per hour — and nothing accelerates it. Coffee, cold showers, food, and exercise affect how awake you feel but not how much alcohol is in your blood. This is why someone can feel considerably better while still being well over the legal limit.
The Widmark equation is a population average and individual variation is large. Body composition, liver enzyme activity, medication, whether you have eaten, and drinking history all shift the outcome. Two people of identical weight and sex can differ by 50 percent or more, which is why no calculator can tell you whether you are safe to drive.
Things worth knowing
- Never use any calculator to decide whether to drive. If you have been drinking, do not drive.
- Food slows absorption but does not reduce the eventual peak or speed elimination.
- The legal limit is 0.08 percent in most US states, 0.05 in much of Europe, and zero for drivers under 21 in the US.
- Drink sizes vary widely. A craft beer at 8 percent is nearly two standard drinks, not one.
- BAC keeps rising for 30 to 90 minutes after your last drink, so a reading taken while drinking understates the peak.
Frequently asked questions
How long does alcohol stay in your system?+
Roughly one standard drink per hour, since elimination runs at about 0.015 percent BAC per hour. A BAC of 0.08 takes around five hours to clear, and nothing speeds that up.
Can I speed up sobering up?+
No. Coffee, water, food, exercise, and cold showers may make you feel more alert but do not change your blood alcohol level. Only time reduces BAC.
Why do women reach a higher BAC than men?+
Because body water distribution differs — women have proportionally less body water, so the same alcohol is less diluted. Lower levels of the gastric enzyme that breaks down alcohol also contribute.
Is this accurate enough to decide if I can drive?+
Absolutely not. Individual variation is large, and no estimate can account for your metabolism, medication, or food intake. If you have consumed alcohol, do not drive.