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BAC Calculator

Blood alcohol estimate by the Widmark formula, over time.

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What you drank

Set how many of each. Volumes and strengths are typical values.

Legal driving limits

LimitWhereYour estimate

Estimated BAC now

—

The curve

Peak (before elimination)—
Pure alcohol consumed—
Standard drinks—
Hours until zero—

Never drive after drinking

No estimate can tell you that you are safe or legal

The Widmark formula uses a population distribution factor. Real values vary with body composition, food, medication, liver function and drinking pattern, so two people who drank identically can differ substantially. Nothing here can tell you whether you are safe or legal to drive, and it must never be used to decide that.

Quick Tool Overview

The BAC Calculator estimates blood alcohol content from your drinks, body weight, sex and elapsed time using the Widmark formula. It shows the curve over time rather than a single instant, and states clearly that no estimate can tell you whether you are safe to drive.

What it does
Estimates blood alcohol content over time
You give it
Drinks, body weight, sex and hours since you started
You get back
Estimated BAC now, the peak and hours until zero
Best for
Understanding how slowly alcohol actually leaves the body
Calculators Free, unlimited use No sign-up Runs in your browser

About the BAC Calculator

Estimate blood alcohol content from what you drank, your body weight and sex, and how long ago you started. The Widmark formula is used, with an elimination rate applied over time so you can see the curve rather than a single instant.

Every estimate of this kind carries an error large enough to matter. Widmark uses a population distribution factor, and real values vary with body composition, food in the stomach, medication, liver function and drinking pattern, so two people who drank identically can differ substantially. Nothing here can tell you whether you are safe or legal to drive, and it should never be used to decide that. The only reliable answer is not to drive after drinking.

Key features of the BAC Calculator

The Widmark formula

The standard forensic model, with an elimination rate of roughly 0.015 percent per hour applied over time.

Drink presets

Pints, wine glasses, spirits and shots with realistic volumes and strengths, or enter your own.

Hours until sober

The figure most people underestimate, shown explicitly alongside the current estimate.

Legal limits listed

The common thresholds of 0.08 and 0.05 percent, with a note that many countries and new drivers are at zero.

Unambiguous safety warning

The page states that individual variation is too large to rely on and that it must never be used to decide whether to drive.

How to use the BAC Calculator

  1. 1

    Add your drinks

    Volume and strength for each, or pick from common presets like a pint of beer or a glass of wine.

  2. 2

    Enter weight and sex

    Both set the Widmark distribution factor, which drives the result.

  3. 3

    Set the elapsed time

    Hours since you started drinking. Alcohol is eliminated at roughly 0.015 percent per hour.

  4. 4

    Read the curve

    Estimated BAC now, the peak, and how long until it reaches zero — as an estimate only.

Frequently asked questions

The Widmark formula divides grams of alcohol by body weight multiplied by a distribution factor, then subtracts elimination at roughly 0.015 percent per hour since drinking began.

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