What this result means
Estimate BAC with a transparent Widmark-style model, pure-alcohol calculation and broad uncertainty warning.
BAC Calculator
Use the BAC Calculator to calculate and interpret estimated BAC.
BAC
Enter your values, then calculate to see a verified result.
Reference range
How this result is calculated
A clear calculation path based on your inputs.
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
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.
Enter the inputsUse values with the units and definitions shown beside each field.
Apply the methodWidmark-style estimate minus 0.015 percentage points per elapsed hour; individual results vary substantially.
Inspect the bridgeReview the primary result and supporting outputs before using it.
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.
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Report a calculation issue BAC Calculator: purpose and method
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.
Keep exploring
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Alcohol Calorie CalculatorEstimate ethanol energy from volume and ABV.Sleep CalculatorCalculate bedtime from wake time and a selected sleep target.Quit Smoking Savings CalculatorEstimate cigarette purchase spending avoided.Sobering Time CalculatorEstimate a broad time-to-zero range from beverage inputs while making clear that no online result makes driving safe.
Method and test recordFormula v1.0.0
- Recorded scope
- BAC Calculator formula, input validation, edge behavior and result presentation.
- Publisher
- CalculatorGeek
- Reviewed by
- CalculatorGeek Editorial Team
- Recorded review date
- 2026-09-21
- Next source review
- 2027-09-21
- Definition fixtures
- 1 configured scenarios
- Published examples
- 1 shown below
Recorded method
Package reconciliation, primary-source mapping, competitor feature comparison, deterministic fixtures, PHP/JavaScript parity and responsive preview QA.
These records describe the published model and reference tests. A test-case count is not a certification of every possible input or an independent specialist review. Editorial policy
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.
Method sources
- NIAAA — What is a standard drink?
- CDC — Impaired Driving
- NIST OSAC — Alcohol calculations in forensic toxicology
- Australian Government — Standard drinks guide
- GOV.UK — Alcohol units
Latest model update
2026-09-21 -
Reference inputs and expected results
Up to 12 examples from the configured definition fixtures are shown. Expected values use the stated output units; invalid inputs are intended to be rejected.
| Case | Inputs | Expected result |
|---|---|---|
| Primary worked example | Body-water estimate: male; Body weight: 80 kg; Drink volume: 355 ml; Alcohol by volume: 5 percent; Number of drinks: 3 value; Hours since first drink: 2 value | Estimated BAC: 0.047225 %; US standard drinks: 3.001018 drinks (allowed numeric tolerance: 0.0001) |
Report an issue with this tool. Include the page URL, units, expected answer, and steps to reproduce. Do not include sensitive personal information.
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.
Continue this workflow with the Alcohol Calorie Calculator. Estimate ethanol energy from volume and ABV.
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.
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
- NIAAA — What is a standard drink?
- CDC — Impaired Driving
- NIST OSAC — Alcohol calculations in forensic toxicology
- Australian Government — Standard drinks guide
- GOV.UK — Alcohol units
Source research refreshed September 21, 2026. No rankings, review credentials or official affiliation are implied.