BAC calculator with standard drinks and a transparent Widmark estimate
Enter actual serving volume, ABV, count, weight and elapsed time. HitEquals estimates pure alcohol, U.S. standard drinks and a Widmark BAC range while keeping the model's limits visible.
Inputs used by this calculator
BAC Calculator uses the fields below. The starting values reproduce the page example; replace them with values from the same units and time period before using the result.
| Input | Starting example | Accepted value | How it is used |
|---|---|---|---|
| Measurement system | US — fluid ounces and pounds | US — fluid ounces and pounds · Metric — milliliters and kilograms | Selects the unit or conversion path used by BAC Calculator. |
| Body-water equation | Male coefficient | Male coefficient · Female coefficient | Supplies the body-water equation quantity used by the published equation or result breakdown. |
| Body weight | 180 | 50 to 1000 | Supplies the body weight quantity used by the published equation or result breakdown. |
| Volume per serving | 12 | 0.1 to 5000 | Supplies the volume per serving quantity used by the published equation or result breakdown. |
| Number of servings | 3 | 0.1 to 50 | Supplies the number of servings quantity used by the published equation or result breakdown. |
| Alcohol by volume (ABV %) | 5 | 0.1 to 100 | Supplies the alcohol by volume (abv %) quantity used by the published equation or result breakdown. |
| Hours since first drink | 2 | 0 to 72 | Supplies the hours since first drink quantity used by the published equation or result breakdown. |
How to use the BAC calculator
Choose the measurement system, enter the label ABV and actual pour size, then add body weight and time since the first drink. Mixed drinks may contain more than one standard serving, so enter the full alcohol volume rather than the glass size alone.
Alcohol and Widmark formulas
The engine converts the beverage to milliliters, multiplies by ABV and an ethanol-density approximation, then applies a sex-specific distribution coefficient. A fixed 0.015 percentage point per hour is a planning assumption rather than a personal metabolism measurement.
alcohol grams=volume mL×servings×ABV÷100×0.789BAC estimate=grams÷(body grams×r)×100−0.015×hoursU.S. standard drinks
NIAAA defines one U.S. standard drink as about 14 grams or 0.6 fluid ounces of pure alcohol. A 12 oz beer at 10% ABV contains about twice the alcohol of a 12 oz beer at 5%.
Why the estimate can be wrong
Real concentration changes with drinking pace, absorption, food, body composition, medications, liver function and biological variation. The coefficient and elimination rate are population assumptions, so two people with identical inputs can have different measured results.
BAC and driving
NHTSA explains that alcohol impairs driving abilities before a person may notice it. Do not use a calculated number, a feeling of sobriety or elapsed time to decide to drive; arrange a sober ride.
When to seek emergency help
Confusion, inability to stay awake, vomiting, seizures, slow or irregular breathing, clammy skin or very low body temperature can signal alcohol overdose. Call emergency services and do not leave the person alone.
Common U.S. standard-drink examples
| Beverage | Serving | Typical ABV |
|---|---|---|
| Regular beer | 12 fl oz | 5% |
| Table wine | 5 fl oz | 12% |
| Distilled spirits | 1.5 fl oz | 40% |
Frequently asked questions
Can this tell me whether I can drive?
No. Never use an estimate to make a driving decision.
What is one U.S. standard drink?
NIAAA defines it as about 14 grams of pure alcohol.
Why does ABV matter?
The same beverage volume can contain very different alcohol doses.
Is 0.015 my exact hourly elimination rate?
No. It is a common model assumption and individual rates vary.
Does food make the alcohol disappear?
No. Food can change absorption timing but does not remove consumed alcohol.
Is a breath test the same as this equation?
No. A properly administered test measures a sample; this page only calculates an estimate.
What to keep in mind
This rough population equation cannot measure your BAC or determine whether driving is safe or legal. Absorption, food, medications, health and individual metabolism can materially change the result. Never drive after drinking.
Results are rounded for display in US format, with money in dollars and cents; CSV exports keep full calculation precision. This is a calculation summary, not an official certificate.