Blood Alcohol Content (BAC) Calculator

drinks
kg
hr
Health

Estimate blood alcohol content (BAC) using the Widmark formula.

Rates and fees change frequently. Always confirm the current figures with the official authority before relying on this result.

Formula

BAC = (drinks × 14) / (weight × r × 1000) × 100 − 0.015 × hours elapsed; r = 0.68 (M) or 0.55 (F)
  • 1 standard drink = 14 g ethanol (US definition).
  • Elimination rate: ~0.015% per hour (0.015 g/100mL/hr) for average adult.
  • This is an estimate only. Actual BAC varies with food intake, tolerance, medications, and individual metabolism.
  • NEVER drive with any measurable BAC.

3 drinks, 70 kg male, 2 hours

Inputs
  • Standard Drinks Consumed: 3 drinks
  • Body Weight: 70 kg
  • Sex: male
  • Hours Since First Drink: 2 hr

BAC = (42)/(70×0.68×1000)×100 − 0.015×2 = 0.088% − 0.030% = 0.058%.

Frequently asked questions

Why is BAC an estimate?
The Widmark formula provides a pharmacokinetic estimate. True BAC depends on gastric emptying, food intake, liver enzyme activity, and individual variation. Only a breathalyser or blood test gives exact BAC.