Blood Alcohol Calculator Estimate Blood Alcohol Concentration (BAC) based on drinks, weight, sex, and time elapsed.

$Blood Alcohol Calculator illustration$

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Blood Alcohol Calculator

Estimate Blood Alcohol Concentration (BAC) based on drinks, weight, sex, and time elapsed.

Enter Your Details

Input body weight, sex, and choose metric or imperial units.

Add Drinks

Select drink type or enter custom size and ABV, then specify quantity.

View BAC Estimate

See estimated BAC, impairment level, and time to sober.

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What Is Blood Alcohol Calculator?

The Blood Alcohol Calculator estimates your Blood Alcohol Concentration (BAC) using the Widmark formula, the standard method for BAC estimation. BAC represents the percentage of alcohol in your bloodstream by volume. The calculator accounts for body weight, biological sex (which affects the distribution ratio of alcohol), number and type of drinks consumed, and hours since your first drink. It includes preset drink types (beer, wine, shots) and custom input options. The tool also estimates time to reach 0.00% BAC based on the average metabolism rate of 0.015% per hour. Important: this is an estimate only and should never be used to determine fitness to drive.

Why Use Blood Alcohol Calculator?

Uses the scientifically established Widmark formula for BAC estimation
Quick-select presets for common drink types (beer, wine, spirits)
Accounts for sex-based differences in alcohol distribution
Estimates time to reach 0.00% BAC

Common Use Cases

Awareness

Understand how alcohol consumption affects your BAC.

Education

Learn about factors that influence blood alcohol levels.

Health & Safety

Make more informed decisions about alcohol consumption.

Reference

Understand BAC levels relative to legal limits.

Technical Guide

BAC is estimated using the Widmark formula: BAC = (A × 5.14 / (W × r)) − 0.015 × H, where A = total alcohol consumed in ounces (drink volume × ABV/100 × number of drinks), W = body weight in ounces, r = sex-based distribution ratio (0.68 for males, 0.55 for females), H = hours since first drink, and 0.015 is the average hourly metabolism rate. The distribution ratio reflects that females typically have higher body fat percentage and lower body water percentage, leading to higher BAC from the same amount of alcohol. This is an estimate — actual BAC varies based on food intake, medications, liver function, genetics, and many other factors.

Tips & Best Practices

1
This is an ESTIMATE only — never use it to determine if you are safe to drive
2
Food in your stomach slows alcohol absorption but does not prevent it
3
The body metabolizes alcohol at approximately 0.015% BAC per hour
4
A standard drink (14g of alcohol) = 12oz beer (5%) = 5oz wine (12%) = 1.5oz spirits (40%)
5
Only time reduces BAC — coffee, water, and food do not speed up alcohol metabolism

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Frequently Asked Questions

Q What is the legal BAC limit?

In the US, the legal limit for driving is 0.08% BAC. Many countries have lower limits (0.05% in Australia, 0.02% in Sweden). Commercial drivers often have a 0.04% limit.

Q How long does it take for alcohol to leave your system?

The body metabolizes alcohol at about 0.015% BAC per hour. A BAC of 0.08% would take approximately 5.3 hours to reach 0.00%.

Q Why does sex affect BAC?

Females generally have a higher body fat percentage and lower body water percentage, causing alcohol to be more concentrated in the bloodstream compared to males of the same weight.

Q Does eating reduce BAC?

Eating before or while drinking slows the rate of alcohol absorption, potentially lowering peak BAC. However, it does not reduce the total amount of alcohol eventually absorbed.

Q Is this calculator accurate?

This provides an estimate using the Widmark formula. Actual BAC depends on many variables including genetics, medications, food, and liver function. Always err on the side of caution.

About This Tool

Blood Alcohol Calculator is a free online tool by FreeToolkit.ai. All processing happens directly in your browser — your data never leaves your device. No registration or installation required.