What Is a BAC Calculator?

A BAC (Blood Alcohol Content) calculator estimates the concentration of alcohol in your bloodstream based on the drinks you've consumed, your body weight, gender, and the time elapsed since you started drinking.

This tool uses the Widmark formula, the most widely accepted method for estimating BAC, which accounts for the body's natural alcohol metabolism rate of approximately 0.015% per hour.

How BAC Is Measured

BAC is expressed as a percentage — the grams of alcohol per 100 milliliters of blood. A BAC of 0.08% means there are 0.08 grams of alcohol per 100ml of blood, which is the legal driving limit in the United States and many other countries.

Why Gender Matters

Men and women process alcohol differently due to differences in body water content. The Widmark formula uses a distribution factor (r) to account for this: 0.68 for men and 0.55 for women. This means that for the same amount of alcohol and body weight, women generally have a higher BAC than men.

Privacy

All calculations are performed entirely in your browser. No information about your drinking habits or personal details is ever sent to any server.

How to Use the BAC Calculator

Follow these simple steps to calculate your estimated blood alcohol content accurately:

Select Your Gender

Choose Male or Female. This determines the Widmark distribution factor used in the calculation.

Enter Your Weight

Use the Metric/Imperial toggle to switch between kg and lbs. The value converts automatically when you switch units.

Enter Hours Drinking

How many hours have passed since your first drink. This accounts for alcohol already metabolized by your body.

Add Your Drinks

Click one of the preset buttons (Beer, Wine, Spirits) to add a standard serving. Click again to increase the quantity, or use the +/− buttons on each item.

Use Custom for Other Drinks

Click the Custom button, enter the volume and ABV%, then click Add.

Read Your Results

Your estimated BAC is displayed prominently with a color-coded impairment level, gauge visualization, time to sober, and US legal limit status.

Adjusting Drinks: Each drink in your list shows the total alcohol content in grams. Use the + and − buttons to adjust quantities, or the ✕ button to remove a drink entirely. Results update in real time as you make changes.

BAC Impairment Levels

Understanding how different BAC levels affect your body and behavior is crucial for making safe decisions. The calculator maps your estimated BAC to one of six impairment levels:

BAC Range	Level	Typical Effects
0.00 – 0.02%	Sober / Minimal	Little to no noticeable effect
0.02 – 0.05%	Slight	Relaxed feeling, mild impairment begins
0.05 – 0.08%	Impaired	Reduced coordination and judgment
0.08 – 0.15%	Legally Drunk	Significant impairment — over the US legal driving limit
0.15 – 0.30%	Severely Impaired	Very dangerous, major loss of control
0.30%+	Danger Zone	Risk of blackout, alcohol poisoning, or death

Widmark Formula

The calculation uses the standard Widmark formula:

Widmark Formula

BAC = (Alcohol grams ÷ (Weight kg × 1000 × r)) × 100 − (0.015 × Hours)

Where r is the Widmark distribution factor (0.68 for men, 0.55 for women), and alcohol grams are calculated as: Volume (ml) × ABV × 0.789 (ethanol density).

Standard Drink Presets

The calculator includes three standard drink presets based on common serving sizes:

Beer

Standard beer serving

330ml volume
5% ABV
~13g alcohol

Wine

Standard wine glass

150ml volume
12% ABV
~14g alcohol

Spirits

Standard shot

44ml volume
40% ABV
~14g alcohol

Custom Drinks: Use the Custom option to enter any drink with a specific volume and ABV percentage for more accurate calculations.

Frequently Asked Questions

How accurate is this BAC calculator?

The Widmark formula provides a reasonable estimate under standard conditions. However, actual BAC can vary significantly based on factors not captured by the formula:

Food intake — Food slows alcohol absorption
Individual metabolism rate — Varies from person to person
Medications — Can affect alcohol processing
Liver health — Impacts alcohol metabolism
Hydration level — Affects blood alcohol concentration

Important: Treat results as estimates only — never make driving or safety decisions based solely on this tool.

Why does gender affect the BAC calculation?

Women typically have a higher percentage of body fat and lower percentage of body water compared to men of the same weight. Since alcohol distributes only in body water, women reach a higher BAC from the same amount of alcohol.

The Widmark formula accounts for this with different distribution factors:

0.68 for men — Higher body water content
0.55 for women — Lower body water content

What does "time to sober" mean?

The time to sober estimate shows how long it will take for your body to metabolize the remaining alcohol, based on the standard rate of 0.015% BAC per hour. This is an average — your actual metabolism rate may be faster or slower.

Remember: The only reliable way to sober up is time; coffee, water, or food do not speed up alcohol elimination.

What is the legal BAC limit for driving?

The calculator displays the US legal limit of 0.08% for reference. Legal limits vary by country and region:

United States: 0.08%
Most of Europe & Australia: 0.05%
Japan: 0.03%
Some countries: Zero-tolerance policies

Always check local laws before driving after consuming any alcohol.

Can I use this to decide whether to drive?

No. This tool provides an estimate only and should never be used to determine if it is safe or legal to drive. Even a BAC below the legal limit can impair your driving ability.

If you have consumed any alcohol, the safest choice is not to drive.