Blood Alcohol Calculator

What Is Blood Alcohol Content?

Blood alcohol content (BAC) measures the amount of alcohol in your bloodstream as a percentage by weight. A BAC of 0.08% means 0.08 grams of alcohol per 100 milliliters of blood – the legal driving limit in most US states. This calculator estimates your BAC based on the number of drinks consumed, your body weight, sex, and the time elapsed since you started drinking. It is intended for educational purposes and should not be used to determine whether you are safe to drive.

How BAC Is Calculated

The Widmark formula is the standard method for estimating BAC. It factors in the total grams of alcohol consumed, body weight, a sex-based distribution ratio (0.73 for men, 0.66 for women), and an elimination rate of approximately 0.015% per hour. Women generally reach higher BAC levels than men at the same weight and alcohol intake because of differences in body water content and alcohol metabolism enzymes. A 160-pound man drinking 3 standard beers over 2 hours reaches roughly 0.06% BAC, while a 130-pound woman drinking the same amount may reach 0.09%.

What Counts as a Standard Drink

In the US, one standard drink contains about 14 grams of pure alcohol. That equals 12 ounces of regular beer (5% ABV), 5 ounces of wine (12% ABV), or 1.5 ounces of distilled spirits (40% ABV). Many popular drinks exceed these measures – a craft IPA at 7% ABV in a 16-ounce pint is closer to 1.5 standard drinks, and a large glass of wine at a restaurant is often 8 to 10 ounces, nearly double a standard serving.

Factors That Affect BAC

Body weight, sex, food in the stomach, rate of consumption, hydration level, and individual metabolism all influence BAC. Drinking on an empty stomach leads to faster absorption and higher peak BAC. Food – especially protein and fat – slows absorption significantly. Carbonated mixers can accelerate alcohol absorption. Medications, fatigue, and altitude can amplify impairment at the same BAC level. Two people drinking the same amount can have very different BAC readings depending on these variables.

BAC Levels and Impairment

At 0.02%, most people feel relaxed with slight mood changes. By 0.05%, judgment and inhibition begin declining noticeably. At 0.08% – the legal limit – reaction time, coordination, and decision-making are significantly impaired. At 0.15%, balance and speech become severely affected. Above 0.30%, loss of consciousness is likely, and BAC levels above 0.40% can be fatal. The only thing that lowers BAC is time – coffee, cold showers, and food do not speed up alcohol metabolism.

Important Disclaimer

This calculator provides an estimate based on averages and cannot account for individual differences in alcohol metabolism, medications, health conditions, or tolerance. Never rely on any BAC calculator to decide whether you are safe to drive. If you have consumed any alcohol, the safest option is always to use a rideshare service, taxi, or designated driver.

Frequently asked questions