Blood Alcohol Content (BAC) Calculator

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Estimate your blood alcohol content from sex, body weight, drinks consumed and time elapsed using the Widmark formula — for education only.

kg
One standard drink ≈ 14 g of pure alcohol.
Estimated BAC – %
Impairment level –
Time to reach 0.00% –
Estimate only — never use this to decide whether to drive. The Widmark formula varies greatly with food, metabolism, medication and health. When in doubt, do not drive.

About Blood Alcohol Content (BAC) Calculator

The Blood Alcohol Content (BAC) calculator estimates the percentage of alcohol in your bloodstream from your sex, body weight, the number of standard drinks you have had and the hours since your first drink. One standard drink is counted as roughly 14 grams of pure alcohol — about one beer, one glass of wine or one shot.

The estimate uses the Widmark formula: the grams of alcohol consumed are divided by your body mass multiplied by a distribution ratio (about 0.68 for men and 0.55 for women), then reduced by a typical elimination rate of 0.015% per hour. The result is shown alongside an impairment level and the approximate time until you return to 0.00%.

It is an educational tool only. Real BAC varies enormously with food, medication, health, fatigue and individual metabolism, so treat every figure as a rough approximation — never as a green light. This free browser-based estimator keeps everything on your device; nothing you enter is sent anywhere.

How to use Blood Alcohol Content (BAC) Calculator

  1. Select your sex and choose metric or imperial units.
  2. Enter your body weight in kilograms or pounds.
  3. Set the number of standard drinks consumed (one drink ≈ 14 g of pure alcohol).
  4. Enter how many hours have passed since your first drink.
  5. Read the estimated BAC, the impairment level and the approximate time to reach 0.00%.

Frequently asked questions

No — never. The result is a rough estimate that can differ significantly from your true BAC. Food, medication, health and metabolism all change the outcome. If you have been drinking, do not drive, regardless of what any calculator shows.

It is the classic BAC estimate: alcohol consumed in grams divided by body weight times a distribution ratio (about 0.68 for men, 0.55 for women), minus roughly 0.015% for each hour of elimination.

About 14 grams of pure alcohol — roughly a 12 oz beer at 5%, a 5 oz glass of wine at 12% or a 1.5 oz shot of 40% spirits. Stronger or larger servings count as more than one drink.

The Widmark formula uses different body-water distribution ratios. Because women on average carry a smaller proportion of body water, the same alcohol produces a higher estimated concentration.

The calculator divides your current estimate by the average elimination rate of about 0.015% per hour. That pace is fixed — coffee, cold showers or exercise do not speed it up; only time sobers you.
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