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BAC Calculator by Weight, Gender, and Drinks

BAC ≈ (grams alcohol ÷ (weight × r)) − 0.015×hours; r differs by sex.

Estimate blood alcohol content from drinks, weight, and time (Widmark). Estimates only—not a diagnosis or prescription.

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Plain-English guide

Terms & how it works

Confused by a field? Read the short definitions here while you use the tool.

  • Standard drinks (14g each)

    The “Standard drinks (14g each)” value used in this tool’s formula. Adjust it to see results update live.

  • Hours since first drink

    The “Hours since first drink” value used in this tool’s formula. Adjust it to see results update live.

  • Weight (lbs)

    The “Weight (lbs)” value used in this tool’s formula. Adjust it to see results update live.

  • Sex (0=F, 1=M)

    The “Sex (0=F, 1=M)” value used in this tool’s formula. Adjust it to see results update live.

How this calculator works

Estimate blood alcohol content from drinks, weight, and time (Widmark). Estimates only—not a diagnosis or prescription. BAC ≈ (grams alcohol ÷ (weight × r)) − 0.015×hours; r differs by sex. Example: 2 drinks, 180 lb male, 2 hr → BAC ~0.03% (estimate only).

BAC ≈ (grams alcohol ÷ (weight × r)) − 0.015×hours; r differs by sex.

Example: 2 drinks, 180 lb male, 2 hr → BAC ~0.03% (estimate only).

When to use this BAC

Common use cases

  • Estimate blood alcohol content from drinks, weight, and time (Widmark).
  • Sanity-check with this case: 2 drinks, 180 lb male, 2 hr → BAC ~0.03% (estimate only).
  • The relationship is: BAC ≈ (grams alcohol ÷ (weight × r)) − 0.015×hours; r differs by sex.

Localized examples

  • Health, Fitness & Wellness: the example on this page uses the same formula as the widget.

What you get

  • Fields: Standard drinks (14g each), Hours since first drink, Weight (lbs), Sex (0=F, 1=M)
  • BAC ≈ (grams alcohol ÷ (weight × r)) − 0.015×hours; r differs by sex.
  • Example on the page: 2 drinks, 180 lb male, 2 hr → BAC ~0.03% (estimate only).

How to Calculate BAC Step-by-Step

  1. 1Enter Standard drinks (14g each), Hours since first drink, Weight (lbs), then the remaining fields. Use the values you have, not a catalog average, unless that is all you know.
  2. 2BAC ≈ (grams alcohol ÷ (weight × r)) − 0.015×hours; r differs by sex.
  3. 3Worked case: 2 drinks, 180 lb male, 2 hr → BAC ~0.03% (estimate only).
  4. 4If this number would change a drug, a diet, or a return-to-play call, take it to a clinician. The page never examined you.

Governing formula

BAC ≈ (grams alcohol ÷ (weight × r)) − 0.015×hours; r differs by sex.

2 drinks, 180 lb male, 2 hr → BAC ~0.03% (estimate only).

Example: set Standard drinks (14g each) = 2, Hours since first drink = 2, Weight (lbs) = 180, then read the result.

Variable definitions

  • standardDrinks

    Standard drinks (14g each)

    The “Standard drinks (14g each)” field. Default 2; typical range 0–15.

  • hoursSince

    Hours since first drink

    The “Hours since first drink” field. Default 2; typical range 0–12.

  • weightLbs

    Weight (lbs)

    The “Weight (lbs)” field. Default 180; typical range 100–350.

  • sex

    Sex (0=F, 1=M)

    The “Sex (0=F, 1=M)” field. Default 1; typical range 0–1.

  • The formula (BAC ≈ (grams alcohol ÷ (weight × r)) − 0.015×hours; r differs by sex.) does not see labs, medications, sleep, or injury history. A clinician does.
  • Nothing here is uploaded for the calculation itself.

Frequently Asked Questions

BAC ≈ (grams alcohol ÷ (weight × r)) − 0.015×hours; r differs by sex.

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4.8

out of 5.0

4 reviews

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Aisha K.

Mar 12, 2026

Clean layout and the results update instantly. Exactly what I needed for a quick planning check.

Daniel R.

Feb 28, 2026

Very usable on mobile. Would love a save/export option later, but the math feels solid.

Priya S.

Feb 3, 2026

The FAQ section answered my questions before I even had to search. Smooth dark mode too.

Marcus L.

Jan 19, 2026

Simple inputs, clear outputs. This replaced three bookmarks I used to juggle.

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