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Blood Alcohol Content Calculator

Estimate blood alcohol content with the Widmark formula. This is for awareness only.

MedicalScience-backed formula
Enter your details
Fill in the fields, then calculate
Important: This estimate is for education only. It cannot tell you it is safe or legal to drive. Many factors change real BAC, and impairment begins before any limit. Never drive after drinking.
Enter your weight.
Enter standard drinks.
Enter hours.

Awaiting Data

Enter your details and tap Calculate to see your results appear here.

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Result

Your result appears here.

What BAC Estimates

Blood alcohol content measures the alcohol in your bloodstream. The Widmark formula estimates it from your drinks, weight, sex, and time.

Your inputs translate into a careful, conservative estimate.

One standard drink holds about 14 grams of alcohol. Your body clears roughly one drink an hour, though this varies widely.

This number is a rough guide, not a legal or medical reading. Food, medication, and metabolism all shift the truth.

How to Use This Calculator

  1. Enter your sex and weight.
  2. Enter standard drinks and hours since the first.
  3. Tap Calculate for an estimate.

The Formula Used

BAC = (alcohol grams / (r × body weight g)) × 100 − 0.015 × hours
r
Body-water constant, 0.68 for men and 0.55 for women.
0.015
Alcohol cleared per hour.

Understanding Your Results

Under 0.03%
Mild
Subtle effects, still impairing.
0.03 to 0.08%
Noticeable
Judgment and coordination drop.
0.08% and above
Legally impaired
The driving limit in many places.
0.30% and above
Dangerous
Risk of severe harm. Seek help.

Tips to Improve

  • Never drive after drinking, at any level.
  • Drink water and eat before and during.
  • Pace yourself to about one drink an hour.
  • Arrange a safe ride home in advance.

Frequently Asked Questions

No. It is an estimate only. Impairment starts before any legal limit, so never drive after drinking.

Roughly 14 grams of alcohol: a 350 ml beer, 150 ml of wine, or 44 ml of spirits.

Weight, sex, food, medication, and metabolism all change how alcohol affects you.

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Scientific References

  1. Widmark, E. M. P. (1932). Die theoretischen Grundlagen der gerichtlich-medizinischen Alkoholbestimmung.
  2. National Highway Traffic Safety Administration. (2023). Alcohol-impaired driving.
  3. Jones, A. W. (2010). Evidence-based survey of the elimination rates of ethanol. Forensic Science International, 200(1-3), 1–20.

Disclaimer: The calculators and information on this site are provided for general informational use only and do not replace professional medical advice, diagnosis, or treatment. Always speak with a qualified healthcare professional about any questions regarding your health.