BAC Calculator

Method, assumptions & sources

Who this is for

Adult educational arithmetic only. Not for legal, clinical or safety decisions.

How it works

Alcohol grams = volume(mL) × ABV/100 × 0.7893 × drink count. Modelled BAC(g/L) = max(0, grams ÷ (r × kg) − 0.15 × max(0, elapsed hours−0.5)); r=0.68 male, 0.55 female. Divide g/L by 10 for % BAC. This is a highly uncertain, fully-absorbed Widmark illustration.

Keep in mind

• A displayed zero does not establish sobriety or safety. Never use this to decide whether to drive, operate machinery or consume more alcohol.
• Actual absorption and elimination vary greatly. No safe-to-drive time or legal-limit clearance is calculated.

Sources

• Terpstra et al. (2020), Appendix A: Widmark model (opens in a new tab)
• NIST: ethanol density (0.7893 g/mL) (opens in a new tab)