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Blood Alcohol Content (BAC) Calculator

Estimate your blood alcohol level based on what you’ve had to drink. Know your limits, plan ahead, and stay safe.

Your estimated BAC
0.055
Mild relaxation

Mild relaxation, slight euphoria, lowered inhibitions.

Nought to 0.40 BAC, always — the axis never rescales
You · 0.055
Under 0.06 0.06 – 0.08 0.08 and over — the US legal limit 0.25 and over

Under the US legal limit of 0.08, and impaired all the same: reaction time and divided attention are measurably worse from about 0.02. Never use this estimate to decide whether to drive.

Back to nought in 3h 41m At the average elimination rate this tool assumes, about 0.015% BAC an hour. Nothing speeds it up.
Which is roughly 4:34 AM On your device’s clock. Individual rates differ, so treat it as the earliest rather than the answer.
Weight
Rounded is fine. A stone either way moves the estimate by a few thousandths, not by a zone.
Biological sex
This picks the Widmark r factor — 0.68 for men, 0.55 for women — because alcohol spreads through body water and the proportion of it differs. The same drinks give a woman a higher BAC at the same weight.
Number of drinks 3 drinks
One standard drink is 12oz of beer, 5oz of wine or 1.5oz of spirits — about 14g of pure alcohol. A large glass of wine is nearer two.
Time spent drinking 2 hours
From the first drink to the last, not the time since you stopped. Your liver has been clearing alcohol the whole way through.
Cleared.

The impairment scale

BACWhat the research describes at that level
0.00 – 0.029 Subtle effects, minimal impairment. You may feel normal.
0.03 – 0.059 Mild relaxation, slight euphoria, lowered inhibitions.
0.06 – 0.079 Judgment and reasoning affected. Reduced coordination.
0.08 – 0.099 Legally drunk in the US. Balance, speech, and reaction time impaired.
0.10 – 0.149 Significant impairment of motor control. Slurred speech, poor balance.
0.15 – 0.199 Serious impairment. Risk of blackout, nausea, loss of muscle control.
0.20 – 0.249 Dangerous. Confusion, vomiting, risk of injury or aspiration.
0.25+ Life-threatening. Loss of consciousness, alcohol poisoning. Call 911.

How this is calculated

This calculator uses the Widmark equation — the standard method for estimating blood alcohol concentration from body weight, biological sex, the amount of pure alcohol consumed, and elapsed time. It assumes a body-water distribution factor (Widmark's "r") of roughly 0.68 for men and 0.55 for women, a US standard drink of 14 g of pure alcohol, and an average elimination rate of about 0.015% BAC per hour. Real BAC varies with genetics, liver function, food, medication and drinking speed, so treat every number here as a rough estimate rather than a measurement.

Sources

Our editorial policy explains how these tools and articles are researched and kept up to date.

Understanding Blood Alcohol Content

The Widmark Formula

This calculator uses the Widmark formula, a well-established method for estimating blood alcohol content developed by Swedish physician Erik Widmark in the 1930s. It remains the standard approach used in forensic toxicology.

The formula accounts for the amount of pure alcohol consumed (each standard drink contains about 14 grams), your body weight, a sex-based distribution ratio (the Widmark r factor: 0.68 for men, 0.55 for women), and the time elapsed while your liver metabolizes alcohol at roughly 0.015% BAC per hour.

The result is an estimate. Real BAC depends on many individual factors this formula cannot capture, so always err on the side of caution.

What Affects Your BAC Besides Drinks

Food intake: Drinking on an empty stomach can produce a BAC up to 3 times higher than drinking after a full meal. Food slows gastric emptying, giving your liver more time to process alcohol before it reaches your bloodstream.

Medications: Many common medications — including antihistamines, antidepressants, painkillers, and antibiotics — can amplify the effects of alcohol or slow its metabolism. Always check drug interactions.

Hydration: Dehydration concentrates alcohol in your blood. Alternating alcoholic drinks with water can slow absorption and reduce peak BAC.

Tolerance vs. BAC: Regular drinkers may feel less impaired, but their BAC is just as high. Tolerance changes how drunk you feel, not how drunk you actually are. This is one of the most dangerous misconceptions about alcohol. It also runs in reverse: the adaptation eases when the drinking stops, which is why people who take a month off — going sober for October, say — often find the same two drinks land harder in November.

Body composition: Muscle tissue contains more water than fat tissue. At the same weight, someone with more muscle mass will generally have a lower BAC because alcohol distributes through water in the body.

BAC and Driving

In the United States, the legal limit for drivers 21 and over is 0.08% BAC in all 50 states. For commercial drivers it’s 0.04%, and for drivers under 21, most states enforce zero-tolerance policies (0.00–0.02%).

International limits vary significantly. Many European countries set the limit at 0.05%, while countries like Sweden, Poland, and Norway use 0.02%. Some countries — including the Czech Republic, Hungary, and several Middle Eastern nations — enforce a strict 0.00% limit.

Impairment begins well below the legal limit. Studies show that reaction time and divided attention are measurably impaired at BAC levels as low as 0.02%. At 0.05%, the risk of a crash is roughly double that of a sober driver.

The safest choice is always to not drive after drinking. Use a rideshare, call a cab, or designate a sober driver. No estimate can guarantee you are safe to drive. That holds the next day too, which is where most people underestimate the arithmetic — the morning after calculator runs the same sum forward from the hour you stopped and prints it as a clock time rather than a countdown.

Asked and answered

Frequently Asked Questions

How accurate is a BAC calculator?
BAC calculators use the Widmark formula, which provides a reasonable estimate. However, actual BAC varies based on genetics, liver function, food intake, medications, and other factors. This is an estimate — not a breathalyzer.
What BAC level is legally drunk?
In most US states, the legal limit is 0.08%. However, impairment begins well below that level. Many countries use lower limits (0.05% or even 0.02%).
How long does it take to sober up?
Your body eliminates alcohol at approximately 0.015% BAC per hour (roughly one standard drink per hour). Nothing speeds this up — not coffee, cold showers, or food. Only time works.
Why does weight affect BAC?
Alcohol distributes through body water. Larger people have more body water to dilute the alcohol, resulting in a lower BAC from the same number of drinks.

Drink Driving Limit

The legal limit where you are and how long alcohol stays measurable. Never a permission to drive.

Alcohol Units Calculator

Any drink turned into UK units and US standard drinks, measured against the weekly guideline.

Alcohol Calories Calculator

The calories in what you drank, shown beside the food you would have to eat to match them.

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