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BAC Calculator

Updated Sep 2026 Used 0 times
A population-average Widmark reference constant; individual physiology varies.
Enter body weight.
Total volume per drink.
ABV shown on the beverage label.
Number of identical servings.
Elapsed time from the first drink.

Guest calculations stay on this device. Signed-in results sync privately.

Your result

BAC

Enter your values, then calculate to see a verified result.

Inputs usedReview the information used for this result.
Full calculation and sourcesWidmark-style estimate minus 0.015 percentage points per elapsed hour; individual results vary substantially.

Versioned calculationFormula v1.0.0

Formula definitionUnit-normalized calculationFormula v1.0.0

What this result means

Estimate BAC with a transparent Widmark-style model, pure-alcohol calculation and broad uncertainty warning.

Method used

Widmark-style estimate minus 0.015 percentage points per elapsed hour; individual results vary substantially.

Important limitation

Widmark inputs and elimination rates are population estimates, not a measurement. The result cannot establish impairment, legal compliance or fitness to drive.

Result actions
1
Enter the inputsUse values with the units and definitions shown beside each field.
2
Apply the methodWidmark-style estimate minus 0.015 percentage points per elapsed hour; individual results vary substantially.
3
Inspect the bridgeReview the primary result and supporting outputs before using it.
4
Check limitationsConfirm the assumptions, date, jurisdiction or population match your use case.

Interpretation

This estimate cannot determine fitness to drive, work, supervise, or make safety decisions.

Widmark-style estimate minus 0.015 percentage points per elapsed hour; individual results vary substantially.

Widmark inputs and elimination rates are population estimates, not a measurement. The result cannot establish impairment, legal compliance or fitness to drive.

Use this result

Keep exploring

2 available tools
Sobering Time CalculatorEstimate a broad time-to-zero range from beverage inputs while making clear that no online result makes driving safe.Standard Drink CalculatorConvert beverage volume and ABV into grams of ethanol plus US, UK and Australian reference units.
Public verification recordFormula v1.0.0
Review scope
BAC Calculator Formula, Input Validation, Edge Behavior And Result Presentation.
Review team
CalculatorGeek Expert Review Team
Verified
2026-09-21
Next source review
2027-09-21
Automated fixtures
1 cases

Review method

Package reconciliation, primary-source mapping, competitor feature comparison, deterministic fixtures, PHP/JavaScript parity and responsive preview QA.

Known limitations

  • Widmark inputs and elimination rates are population estimates, not a measurement. The result cannot establish impairment, legal compliance or fitness to drive.
  • Changing legal, medical, exam or statistical conventions must be checked at the source.

Primary sources

Latest update

2026-09-21 ·

On this page

Direct answer

Estimate BAC with a transparent Widmark-style model, pure-alcohol calculation and broad uncertainty warning.

Continue with the Sobering Time Calculator when that method matches your next question.

Continue with the Standard Drink Calculator when that method matches your next question.

Formula and methodology

Widmark-style estimate minus 0.015 percentage points per elapsed hour; individual results vary substantially.

This estimate cannot determine fitness to drive, work, supervise, or make safety decisions.

Continue with Sobering Time Calculator or Standard Drink Calculator for the next calculation.

Worked example

This estimate cannot determine fitness to drive, work, supervise, or make safety decisions.

The calculator retains working precision and rounds only the displayed values.

Interpret the result carefully

Method boundary: Widmark inputs and elimination rates are population estimates, not a measurement. The result cannot establish impairment, legal compliance or fitness to drive.

Inputs, boundary behavior and JavaScript/PHP parity are covered by deterministic release tests.

Use the result for the named task only. Do not stretch it into a legal, clinical, safety or causal conclusion the formula does not support.

Inputs, outputs and result meaning

Calculates estimated BAC, estimated peak BAC, uS standard drinks, and average hours to zero from body-water estimate, body weight, drink volume, and alcohol by volume with visible method, validation, precision, and limitations.

Inputs

Body-water estimate
A population-average Widmark reference constant; individual physiology varies. Available choices are Male reference constant and Female reference constant.
Body weight
Enter body weight. Supported units include kg. The supported range is 25 through 400.
Drink volume
Total volume per drink. Supported units include mL. The supported range is 1 through 10,000.
Alcohol by volume
ABV shown on the beverage label. Supported units include %. The supported range is 0 through 100.
Number of drinks
Number of identical servings. The supported range is 0 through 100.
Hours since first drink
Elapsed time from the first drink. The supported range is 0 through 72.

Outputs

Estimated BAC
This is the primary result. It is displayed in %. The visible value uses up to 4 decimal places according to the output rule.
Estimated peak BAC
It is displayed in %. The visible value uses up to 4 decimal places according to the output rule.
US standard drinks
It is displayed in drinks. The visible value uses up to 3 decimal places according to the output rule.
Average hours to zero
It is displayed in hours. The visible value uses up to 2 decimal places according to the output rule.

The calculator applies the documented method after validating and normalizing the inputs. Keep the result label, unit, selected mode, and stated limitations together when sharing the answer.

Frequently asked questions

What method does this calculator use?

Widmark-style estimate minus 0.015 percentage points per elapsed hour; individual results vary substantially.

How should I round the result?

Keep full precision during the calculation and round only the final display unless a governing standard says otherwise.

What is the main limitation?

Widmark inputs and elimination rates are population estimates, not a measurement. The result cannot establish impairment, legal compliance or fitness to drive.

Can I reproduce the answer?

Yes. The formula, inputs, supporting outputs and worked example are displayed on the page.

Sources

Source research refreshed September 21, 2026. No rankings, review credentials or official affiliation are implied.