Health & Fitness

BAC Calculator

The BAC Calculator estimates blood alcohol content from your sex, body weight in pounds, number of standard drinks, and hours since your first drink using the Widmark formula.

What this calculator does

The BAC Calculator estimates your result instantly from the values you enter, using standard health & fitness formulas. The BAC Calculator estimates blood alcohol content from your sex, body weight in pounds, number of standard drinks, and hours since your first drink using the Widmark formula. Calculations run in your browser, so nothing you type is sent to a server, and the output is an estimate rather than a certified or official figure.

Blood Alcohol Content (BAC) Calculator

Result

0.000%
Estimated Blood Alcohol Content

This tool is for general informational purposes only and is not a substitute for professional medical advice.

About BAC Calculator

This Blood Alcohol Content calculator uses a Widmark-based formula, converting standard drinks to ounces of pure alcohol and subtracting the alcohol metabolized over the hours since your first drink.

It reports a single estimated BAC percentage. When that estimate reaches 0.08%, the tool notes this is the U.S. legal driving limit.

Formula & Mathematical Calculation

alcoholOz = drinks × 0.6

bac = (alcoholOz × 5.14 ÷ (weight × r)) - (0.015 × hours)

Derived directly from the verified calculation function in the tool engine.

Calculation Example

For a male of 180 lbs after 3 drinks over 2 hours: alcohol = 3 × 0.6 = 1.8 oz, and r = 0.68.

BAC = 1.8 × 5.14 ÷ (180 × 0.68) − 0.015 × 2 = 9.252 ÷ 122.4 − 0.03 ≈ 0.0756 − 0.03 = 0.046%.

Key Benefits

  • Uses the Widmark formula with sex-specific factors of 0.68 and 0.55.
  • Converts each standard drink to 0.6 ounces of pure alcohol.
  • Subtracts alcohol metabolized at 0.015 percent per hour since the first drink.
  • Flags when the estimate reaches the 0.08% U.S. legal driving limit.

How to Use this Calculator

  1. Select sex
    Choose Male or Female.
  2. Enter weight
    Type your body weight in pounds.
  3. Enter drinks and hours
    Enter the number of standard drinks and the hours since your first drink.
  4. Calculate and read
    Select Calculate and read the Estimated Blood Alcohol Content value.

Assumptions & Limitations

What the calculation assumes

  • Every value you enter is treated as an exact, known amount.
  • Any rate or interval you enter is assumed to hold for the whole period unless the form asks for it separately.
  • Results use standard published formulas and account only for the values entered above.
  • Rounding is applied for display; the underlying calculation uses your full precision.
  • Results are returned in the same units you enter, unless the tool states the output unit.

What it does not cover

  • BAC Calculator produces a calculated result for reference and learning, not a certified or official measurement.
  • Real-world outcomes differ when tolerances, rounding rules or local standards apply.
  • Definitions and standards vary by region and change over time; verify the convention that applies to your case.
  • Figures are only as accurate as the inputs you supply — check them before acting on the result.
  • For work where the result carries real consequences, confirm it against an authoritative source.

Frequently Asked Questions

The tool treats each standard drink as 0.6 ounces of pure alcohol.

It subtracts 0.015 percent per hour since the first drink to account for metabolism.

The formula uses r = 0.68 for males and 0.55 for females.

No; it is a rough estimate and real BAC varies with metabolism, food, and other factors, so the tool states it should not be relied on for that decision.

Free to use, no account needed. Calculations run in your browser, so nothing you type is sent to a server. Results are estimates — how we build and check our calculators.