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Blood Alcohol Concentration (BAC) Calculator

Estimated BAC using the Widmark formula.

Estimate Blood Alcohol Concentration (BAC) using the Widmark formula, given the number of standard drinks, body weight, sex (which sets the body water factor r), and elapsed hours since the first drink.

Priya Venkatesan By Priya Venkatesan
Reviewed by Dr. Helena Ortiz
Published Last reviewed 1 min read

Inputs

kg

Results

Enter values and click Calculate to see results.
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How to use this calculator

  1. Fill in the inputs above using the units you already have.
  2. Values update automatically as you type — no submit button needed.
  3. Hover any result row for the underlying formula and intermediate values.

Formula

BAC % = (drinks · 14 · 100) / (weight_g · r) − β · hours, β ≈ 0.015 %/h.

In depth

Estimate Blood Alcohol Concentration (BAC) using the Widmark formula, given the number of standard drinks, body weight, sex (which sets the body water factor r), and elapsed hours since the first drink.