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Blood Alcohol Content Calculator

Estimate your blood alcohol content from your sex, body weight, how much you drank, and how long ago you started. An estimate, never a measurement.

Sex

Units

Calculated in your browser. Nothing is uploaded.

Enter drinks as

One standard drink is about 14 g of pure alcohol: a 12 oz 5 percent beer, a 5 oz 12 percent wine, or a 1.5 oz 40 percent spirit.

Enter your weight and drinks to estimate your blood alcohol content.

This is a rough estimate, not a measurement, and it can be wrong in either direction. Food, pace, medication, and individual differences all change your real level. Never use it to decide whether it is safe to drive. If you have been drinking, do not drive.

How to estimate your blood alcohol content

  1. Enter your details

    Choose your sex and enter your body weight in metric or imperial units.

  2. Add your drinks

    Enter how many standard drinks you have had, or switch to volume and ABV for an exact pour, then set how many hours ago you started.

  3. Read the estimate

    Your estimated blood alcohol content, an impairment note, and the time until it returns to 0.00 appear instantly; use Copy summary to save it.

Why use this tool

Widmark estimate

Uses the Widmark formula with sex-based body water factors and a steady clearance rate to estimate the alcohol in your bloodstream right now.

Standard drinks or exact pour

Count standard drinks, or enter the precise volume and ABV of what you drank for a closer estimate.

Impairment at a glance

Every estimate comes with a plain description of the likely effects and a flag once you pass the common 0.08 percent driving limit.

Time back to zero

See roughly how long until your estimated blood alcohol returns to 0.00, based on a clearance of about 0.015 percent per hour.

Estimate, not a measurement

The result carries a clear reminder that it is only an estimate and must never be used to decide whether to drive.

Runs entirely in your browser

Everything is calculated on your device. Nothing you enter is uploaded or stored.

About this tool

This blood alcohol content calculator estimates the alcohol in your bloodstream from four things: your sex, your body weight, how much you have had to drink, and how long ago you started. It applies the Widmark formula, the same approach behind most BAC charts, spreading the alcohol you drank across your body water and then subtracting what your body clears over time at a steady rate of about 0.015 percent per hour.

Enter your weight in kilograms or pounds and either a count of standard drinks or the exact volume and strength of what you drank. One standard drink counts as 14 grams of pure alcohol, roughly a 12 oz 5 percent beer, a 5 oz 12 percent wine, or a 1.5 oz 40 percent spirit. The estimate updates as you type, alongside a plain impairment note and the time it should take to return to 0.00. For related body maths, try the BMI calculator, and the unit converter handles standalone weight and volume conversions.

Treat the result as a rough estimate, not a measurement. Real blood alcohol depends on food, drinking pace, medication, hydration, health, and individual differences the formula cannot see, so your true level can be higher or lower. Never use this tool to decide whether it is safe to drive. If you have been drinking, do not drive.

Frequently asked questions

How is blood alcohol content calculated here?
The tool uses the Widmark formula. It works out the grams of pure alcohol you drank, divides that by your body weight multiplied by a body water factor of 0.68 for men or 0.55 for women, converts to a percentage, and then subtracts about 0.015 percent for every hour since your first drink.
What counts as a standard drink?
In standard drinks mode, one drink is treated as 14 grams of pure alcohol. That is roughly a 12 oz beer at 5 percent, a 5 oz glass of wine at 12 percent, or a 1.5 oz shot of spirit at 40 percent. If your drinks differ, switch to volume and ABV mode and enter the exact amount and strength.
How accurate is the estimate?
It is only an estimate. Food, drinking pace, sex, medication, hydration, and individual metabolism all affect real blood alcohol, and none of them are fully captured by a single formula. Your true level could be meaningfully higher or lower, so treat the number as a rough guide, not a reading.
Can I use this to decide whether I can drive?
No. This is an estimate, not a breathalyzer or blood test, and it can be wrong in either direction. The only safe amount of alcohol before driving is none. If you have been drinking, do not drive, regardless of what any calculator shows.
What does the time to 0.00 mean?
It is a rough estimate of how much longer until the alcohol clears from your bloodstream, assuming your body removes about 0.015 percent per hour and you drink nothing more. Nothing speeds this up: not coffee, water, food, or a cold shower. Only time lowers blood alcohol.
Is my data uploaded anywhere?
No. Everything runs in your browser; nothing is sent to a server. The details you enter are used only to calculate the estimate on your device and are never uploaded, stored, or logged.

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