BAC Calculator

How high is your BAC after drinking? Use our blood alcohol content calculator to find out. Based on the Widmark formula, it accounts for your weight, biological sex, drink type, and time to give you an accurate estimate. Whether you had beer, wine, or spirits, our BAC calculator shows your current level and impairment status.

Wondering how long until your BAC reaches 0.00%? Your liver metabolizes alcohol at approximately 0.015% per hour — about one standard drink per hour. Our sobriety calculator shows exactly how long it will take based on your current estimated BAC level, so you can plan ahead for when it's safe to drive.

Body weight and biological sex significantly affect BAC. A 120 lb woman will reach a much higher BAC than a 220 lb man after the same number of drinks. Our BAC calculator by weight uses sex-specific Widmark factors (0.68 male, 0.55 female) for more accurate results tailored to your body.

Blood alcohol content is estimated with the Widmark formula, which divides the pure alcohol you drank by the amount of water your body can distribute it into. In short, the same drinks produce a higher BAC in a smaller person because there is less body water to dilute the alcohol.

The formula multiplies your body weight by a distribution factor (about 0.68 for men and 0.55 for women), then subtracts the alcohol your liver has already burned off over time.

Three inputs drive the result:

• Grams of pure alcohol consumed, derived from drink count, serving size, and ABV
• Body weight and sex, which set your total body water
• Hours elapsed, multiplied by the metabolism rate to remove processed alcohol

The National Institute on Alcohol Abuse and Alcoholism (NIAAA) describes this body-water difference as a key reason BAC varies between individuals.

Enter your weight, sex, drinks, and time, and the calculator returns an estimated BAC in seconds. Consider a 180 lb man who has three standard beers over two hours.

First, the tool converts three beers into grams of pure alcohol. Each standard drink holds roughly 14 grams of alcohol, so three beers is about 42 grams — a figure consistent with the standard-drink definition published by NIAAA and the CDC.

Next it applies the Widmark math and subtracts two hours of metabolism.

• Weight and sex set the distribution factor
• 42 grams of alcohol enter the numerator
• Two hours elapsed removes roughly 0.03% BAC

The result is about 0.045% BAC — below the common 0.08% driving limit but still enough to impair judgment and reaction time.

The most common mistake is treating a BAC estimate as an exact, safe-to-drive reading. A calculator uses population averages, so your true BAC can be meaningfully higher or lower.

Other frequent errors distort the input before the math even begins.

• Counting drinks, not standard drinks — a large craft beer or a strong cocktail can equal two or more standard drinks
• Ignoring serving strength — a 7% IPA or an overpoured spirit raises alcohol grams sharply
• Assuming coffee, water, or a cold shower speeds sobering — the CDC and NIAAA are clear that only time lowers BAC
• Forgetting rising BAC — your level can keep climbing for 30 to 90 minutes after your last drink
• Overlooking medications, which the U.S. Food and Drug Administration (FDA) warns can amplify alcohol's effects

When in doubt, do not drive.

A standard drink in the United States contains about 14 grams (0.6 ounces) of pure alcohol, the benchmark used by the National Institute on Alcohol Abuse and Alcoholism (NIAAA) and the CDC. Getting this right is essential, because BAC math depends on grams of alcohol, not on how many glasses you held.

Equal-alcohol servings look very different:

• 12 oz of regular beer at about 5% ABV
• 5 oz of table wine at about 12% ABV
• 1.5 oz of distilled spirits at about 40% ABV

Many real-world pours exceed one standard drink.

• A pint of strong IPA can be 1.5 or more standard drinks
• A restaurant wine pour often exceeds 5 oz
• A mixed cocktail may hide two or three shots

Use the custom ABV and serving fields to reflect what you actually drank.

Impairment begins well before the legal limit — even a BAC around 0.02% measurably affects judgment and multitasking, according to safety data from the National Highway Traffic Safety Administration (NHTSA) and the CDC.

BAC effects escalate as the number rises.

• 0.02% — mild relaxation, some loss of judgment and divided attention
• 0.05% — reduced coordination, lowered alertness, slower response to emergencies
• 0.08% — the legal driving threshold in most US states; clear loss of muscle control and reasoning
• 0.15% and above — major impairment of balance, vision, and self-control, with rising health risk

Because tolerance can mask these signs, feeling "fine" is not a reliable gauge.

The NIAAA notes that a BAC near 0.31% or higher can be life-threatening. Treat high estimates as a medical warning, not a challenge.

In most US states the legal BAC limit is 0.08% for drivers 21 and older, a threshold reflected in guidance from the National Highway Traffic Safety Administration (NHTSA). Some jurisdictions, including Utah, set a lower 0.05% limit, so always confirm the rule where you are.

Stricter limits apply to specific drivers.

• Commercial drivers are typically held to a 0.04% limit
• Drivers under 21 face zero-tolerance laws, often 0.00% to 0.02%

Importantly, you can be charged with impaired driving below 0.08% if an officer observes impairment.

The CDC emphasizes that no BAC level is proven safe for driving. A calculator estimate cannot account for your real blood alcohol level, so it should never be the basis for deciding to get behind the wheel.

Eating before drinking slows how fast alcohol enters your bloodstream, which can lower your peak BAC — but it does not prevent intoxication. The NIAAA notes that food, especially higher-protein and higher-fat meals, delays absorption rather than removing alcohol.

Several personal factors shift your real BAC away from the calculator's average.

• An empty stomach leads to faster, higher BAC peaks
• Liver health and genetics change how quickly you metabolize alcohol
• Hydration and body composition alter alcohol distribution, so knowing your daily target from a water intake calculator can help you rehydrate sensibly afterward
• Medications — the FDA warns that many prescription and over-the-counter drugs interact dangerously with alcohol

Metabolism itself is roughly fixed near 0.015% BAC per hour and cannot be sped up by coffee, exercise, or fresh air.

Because these variables are individual, treat any BAC estimate as a rough guide, not a precise reading.

A BAC calculator gives a scientific estimate, not a measurement — your true blood alcohol level can differ substantially from the number shown. The Widmark method relies on population averages for body water and a typical metabolism rate, and it cannot see your genetics, meals, medications, or liver function.

The estimate is most useful for planning and education, and least useful for high-stakes decisions.

• Reasonable use — understanding roughly how drinks accumulate and how long sobering may take
• Unsafe use — deciding whether you are legally clear to drive

Only a breathalyzer or blood test can measure actual BAC, and even those have their own conditions.

Both the CDC and NIAAA stress that if you have been drinking, the safe choice is to arrange another way home. When in doubt, do not drive.