Blood Alcohol Content (BAC) Calculator
Estimate your blood alcohol content using the Widmark formula. See your current BAC, peak BAC, impairment level, and time to sobriety based on drink type, body weight, and gender.
About this calculator
This calculator estimates blood alcohol content using the Widmark formula, a century-old model still taught in toxicology and used in forensic estimation today: it converts your drinks into grams of pure ethanol consumed, then divides that by your body weight and a sex-specific distribution ratio — the Widmark factor — that approximates how alcohol disperses through body water, which differs on average between men and women due to typical differences in body composition. That calculation gives peak BAC, the highest level alcohol reaches shortly after drinking stops, before the liver has had meaningful time to metabolize any of it. From there, the calculator subtracts a standard elimination rate of about 0.015% BAC per hour — a widely cited average metabolism rate — to estimate current BAC and project how many hours remain until BAC returns to zero.
Every number here is a population-average estimate, not a measurement: real BAC is affected by factors this formula can't capture, including how much food was in your stomach, how quickly you drank rather than just how much, individual differences in liver enzyme activity, medications, and even the specific ABV of what you actually drank versus the typical values assumed for beer, wine, and spirits here. Because of that irreducible uncertainty, this estimate should never be used to decide whether it's safe to drive, operate machinery, or that you are under a legal limit — actual BAC can run meaningfully higher than a formula-based estimate suggests, and impairment itself begins well before any legal threshold.
Medical Disclaimer
This calculator is for informational and educational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider before making decisions about your health. Never disregard professional medical advice or delay seeking it because of results from this tool.
Inputs
Results
Current BAC
0.0651
How to Use This Calculator
- Enter your body weight in pounds.
- Select your biological sex (affects alcohol metabolism rate).
- Enter the number of drinks you have consumed.
- Select the type of drink (beer, wine, or spirits) to determine alcohol content.
- Enter the number of hours since you started drinking.
- Review your estimated BAC, legal status, impairment level, and time to sobriety.
- Use the chart to see how your BAC decreases over time as your body metabolizes alcohol.
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How the result changes with Body Weight
| Body Weight | Current BAC |
|---|---|
| 112 | 0.1066 |
| 192 | 0.0559 |
| 288 | 0.0323 |
| 368 | 0.022 |
What each input means
- Body Weight
- Your body weight in pounds.
- Biological Sex
- Biological sex affects the Widmark factor used in BAC estimation.
- Number of Drinks
- Total number of drinks consumed.
- Drink Type
- The type of alcoholic beverage consumed.
- Hours Since Drinking
- Time elapsed since you started drinking.
How this is calculated
Worked example, using the default values
- Identify Input Parameters5 parametersBody Weight = 170 lbs, Gender = Male, Drinks = 3, Drink Type = Beer (12 oz, 5%), Hours = 1 = 5 input(s) provided
- Calculate Alcohol Consumed (grams)alcoholGrams = drinks × sizeOz × 29.5735 × ABV × 0.7893 × 12 × 29.5735 × 0.05 × 0.789 = 42 g
- Calculate Peak BAC (Widmark formula)peakBAC = alcoholGrams / (bodyWeight × 453.592 × r)42 / (170 × 453.592 × 0.68) = 0.0801
- Apply Metabolism Over TimeBAC = peakBAC − (0.015 × hours)0.0801 − (0.015 × 1) = 0.0651
- Estimate Time to SobertimeToSober = currentBAC / 0.0150.0651 / 0.015 = 4.34 hours
Engine last updated . Checked against 3 independently-derived tests — how we verify calculators.
Frequently Asked Questions
Why does the calculator ask for biological sex, and does that assumption always hold?
The Widmark formula uses a different distribution ratio for men and women — 0.68 versus 0.55 in this calculator — because alcohol disperses through body water, and men on average have a higher proportion of body water relative to total body weight than women do, which means the same amount of alcohol reaches a higher concentration in a body with less water to dilute it into. These are population averages, though, and an individual's actual body composition can differ substantially from the sex-based average the formula assumes, which is one of several reasons this remains an estimate rather than a precise measurement.
Why can two people who drank the exact same amount end up with noticeably different actual BAC?
Body weight and sex-based distribution ratio are only part of the real picture — how much food was eaten beforehand, how quickly the drinks were consumed, individual metabolic and liver enzyme differences, medications, and even genetics all measurably affect how alcohol is absorbed and processed, none of which a formula based only on weight, sex, and drink count can capture. This is exactly why two people with identical inputs to this calculator can have meaningfully different real BAC levels in practice.
Is it safe to drive once this calculator shows a BAC under the legal limit?
No — this is an estimate with real uncertainty in both directions, and actual impairment to reaction time, judgment, and coordination begins well below the legal BAC threshold in most places, not just once you cross it. The only genuinely safe choice after drinking is not to drive at all; this calculator is meant for general education about how alcohol metabolism works, not as a tool for deciding whether driving is safe.
Why does 'time to sober' only track BAC reaching zero, not when it's actually safe to drive?
The 0.015% per hour elimination rate estimates when the body has fully metabolized the alcohol consumed, but impairment to judgment, reaction time, and coordination can persist even as BAC approaches zero, and residual effects like fatigue from a night of drinking can impair driving ability independent of measurable blood alcohol at all. Reaching an estimated zero on this calculator is not the same thing as being fully recovered or safe to perform tasks that require full alertness.
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