» BAC Calculator: Blood Alcohol Content Estimate


BAC calculator to estimate blood alcohol content from drink volume, ABV, body weight, sex, and time since drinking started using the Widmark formula.

Use this BAC calculator to estimate blood alcohol content from the total drink amount, alcohol by volume (ABV), body weight, sex, and time since drinking started. The calculator uses the Widmark formula and lets you switch the result between common BAC units.

This page is best for quick BAC estimates after beer, wine, spirits, cocktails, or any drink where you know the volume and strength. The result is only a rough estimate because real blood alcohol concentration can also be affected by food intake, metabolism, medications, hydration, body composition, and how quickly the drinks were consumed.

Widmark formula

$$BAC \approx \frac{A}{r \times W} - \beta \times t$$

A = pure alcohol in grams,
W = body weight in kilograms,
r = Widmark distribution factor,
t = hours since drinking started,
β = alcohol elimination rate used for the estimate.

This calculator uses the Widmark approach for a rough estimate only. Actual BAC can vary because of food intake, metabolism, medications, body composition, and drinking pattern.

Sources: Hustad JT, Carey KB (2005); Peck RC et al. (2008).

Initial Data

Note: Notice! The calculator result is an approximate! The calculator does not take into account person's physical characteristics (such as body composition, metabolism), health, physical activity and nutrition. The result of calculation can differ from a blood sample or BAC measurement results.
Drink input mode



Result

Pure alcohol 0.0 g
Standard drinks equivalent 0.00
BAC (%) 0.0000%
BAC (‰) 0.0000‰
Estimated time until BAC reaches 0 0h 00m
Estimated time until below legal limit
 0h 00m
0.08% BAC (0.8 promille)

Estimated BAC effects

Enter your values to see the estimated BAC range.

BAC (%) Result
0.00-0.029 Subtle effects may begin. Attention and judgment can already be reduced.
0.03-0.059 Relaxation and reduced inhibition are common, with measurable impairment beginning to increase.
0.06-0.099 Judgment, coordination, reaction time, and visual tracking are often impaired.
0.10-0.149 Speech, balance, motor control, and reasoning are commonly affected.
0.15+ Severe impairment is possible, including blackout risk and medical danger at higher levels.

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BAC Calculator FAQ

What is BAC?
BAC means blood alcohol content or blood alcohol concentration. It is usually expressed as the amount of alcohol present in the blood, often as a percentage or per mille value.

How does this BAC calculator work?
This calculator estimates BAC with the Widmark formula. It combines the total amount of alcohol consumed, your body weight, sex, and the time since drinking started, then applies an estimated alcohol elimination rate.

Is this blood alcohol calculator accurate?
No online blood alcohol calculator can be exact for every person. Food, metabolism, medication, body composition, health conditions, and drinking speed can change the real result, so treat the number as an estimate only.

Can coffee, water, or a cold shower lower BAC faster?
No. Coffee, water, food, and cold showers may change how you feel, but they do not reliably reduce BAC. Time is the main factor that lowers blood alcohol concentration.

Can I use this result to decide if I can drive?
No. Legal BAC limits vary by country, state, vehicle type, age, and license status. Do not rely on an online BAC estimate to decide whether it is safe or legal to drive.

Is one 4 cl spirit shot equal to one gin and tonic, rum and cola, or mojito?
Not automatically. They are only roughly equivalent if the cocktail contains about the same amount of pure alcohol as the shot. A 4 cl shot at 40% contains about 12.6 g of pure alcohol. A gin and tonic, rum and cola, or mojito can be similar if it uses roughly one 4 cl measure of 40% spirit, but the real amount depends on the recipe and pour size.


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