Advanced BAC Calculator – Accurate Alcohol Estimation

Estimate your BAC

Enter your details and drinks to see an approximate blood alcohol concentration. Results are only estimates and must not be used to decide if you can drive.

Sex

Body weight

Use an approximate value if you are not sure. The estimate is sensitive to body weight.

Country or region

This helps us compare your estimated BAC with commonly cited legal limits in your selected region.

Time since your first drink

hours

minutes

Count from the first sip of your first drink. The longer you have been drinking, the lower your BAC may be from metabolism.

Drinks you have consumed

Drink 1

Type

Number of servings

Serving size (mL)

ABV (%)

%

Never use BAC estimates to decide whether you can drive.

Estimated BAC and safety overview

These numbers are only rough estimates. Everyone processes alcohol differently.

Fill in your details and drinks, then select “Estimate BAC” to see estimated values and safety guidance.

How to get a more accurate BAC estimate

Standard calculators often fail because users enter '1 beer' without knowing its size or strength. To use this tool like a pro, check the label on your bottle for the exact volume (mL) and alcohol percentage (ABV).

The impact of food (Advanced)

Food delays gastric emptying, which slows down the rate alcohol enters your bloodstream. While most calculators (including this one) give a 'worst-case' estimate based on an empty stomach, eating a full meal before drinking can lower your peak BAC. Keep this in mind: the calculator shows your potential maximum.

The Widmark Formula explained

This tool uses the advanced Widmark formula, which accounts for the distribution of alcohol in the whole body water. It uses specific constants for men (0.68) and women (0.55) to determine how diluted the alcohol becomes in your system. While some users search for the 'Celtic BAC calculator' method, the Widmark formula remains the global standard for forensic alcohol estimation.

Limitations of advanced calculation

Even an advanced calculator cannot measure your individual liver function or genetic metabolic rate. These biological variables can cause your actual BAC to vary by +/- 0.02% or more from the estimate.

Advanced Calculator FAQ

We use the scientifically validated Widmark formula, which is the gold standard for estimation. However, without a blood test, no online tool is 100% perfect due to individual biological variations.

Don't guess. Ask the bartender how much spirit was used (e.g., 45ml or 60ml) and enter that as a 'Spirits' drink with the correct ABV (usually 40%). Ignoring the mixer volume is fine as it doesn't contain alcohol.

Yes. Alcohol does not dissolve in fat. A person with higher body fat has less body water per kg of weight, leading to a higher BAC. Our calculator uses average body composition data for your sex.