BAC Calculator - Blood Alcohol Content & Sobriety Estimator

Here's what you'll need:

• Number of drinks: Count each standard drink separately. In the U.S., a standard drink is 12 oz of regular beer (5% ABV), 5 oz of wine (12% ABV), or 1.5 oz of spirits (40% ABV).
• Body weight: Enter your weight in pounds. This has a bigger impact on your result than most people expect.
• Gender: Biological sex affects how your body distributes and processes alcohol, so select male or female.
• Hours drinking: How long have you been drinking? The longer the window, the more alcohol your liver has had time to metabolize.

Hit calculate and the tool runs the Widmark formula (more on that in a moment) to give you an estimated BAC percentage and a general sense of your impairment level.

Your result will show up as a decimal, something like 0.08% or 0.12%. That number represents grams of alcohol per 100 milliliters of blood.

A result of 0.00% means you're at or near zero. Anything above 0.08% puts you at or over the legal driving limit in every U.S. state. Higher numbers mean more impairment, full stop. There's a chart further down that breaks out what different BAC levels actually feel like and what risks they carry.

If your estimated BAC is above 0.00% and you're wondering when you'll be back to zero, scroll down to the sobriety timeline section. Your body clears alcohol at a fairly predictable rate, and we'll walk through how to estimate it.

For men, the Widmark formula looks like this:

BAC = (Alcohol consumed in grams / (Body weight in grams × 0.68)) × 100 − (0.015 × Hours elapsed)

The constant 0.68 is the Widmark factor for men. It represents the share of body weight made up of water-containing tissue that absorbs alcohol. Men generally carry more lean muscle and less body fat than women at the same weight, so alcohol gets diluted across a larger volume of tissue.

The formula for women is the same structure, just with a different Widmark factor:

BAC = (Alcohol consumed in grams / (Body weight in grams × 0.55)) × 100 − (0.015 × Hours elapsed)

The factor 0.55 reflects a lower proportion of water-containing tissue. Women tend to carry a higher percentage of body fat relative to total weight, and fat doesn't absorb alcohol the way muscle does. So the same amount of alcohol spreads through a smaller effective volume, which pushes BAC higher.

Let's run through a real example. A 160-pound man, 3 standard drinks, over 2 hours.

1. Convert weight to grams: 160 lbs × 453.592 = 72,575 grams
2. Calculate grams of alcohol: Each standard drink has about 14 grams of pure alcohol. 3 drinks × 14g = 42 grams
3. Apply the Widmark formula: BAC = (42 / (72,575 × 0.68)) × 100 = (42 / 49,351) × 100 ≈ 0.085%
4. Subtract metabolism: 0.085 − (0.015 × 2 hours) = 0.085 − 0.030 = 0.055%

After 2 hours, that person's estimated BAC is around 0.055%. Under the legal limit, yes, but still enough to affect judgment and reaction time. Not a number to brush off.

On average, the liver clears alcohol at about 0.015% BAC per hour. That's the standard figure used in the Widmark formula and it's backed by decades of research.

In practical terms: stop drinking at 0.09% and it'll take roughly 6 hours to reach zero. Some people metabolize a bit faster or slower depending on liver health, genetics, and drinking habits, but 0.015% per hour is a solid, conservative estimate for most adults.

There's no shortcut. Sleeping it off works only because sleep takes time. Your BAC keeps dropping while you sleep at the exact same rate it would if you were awake.

The table below gives rough estimates for how long it takes a 160-pound man to reach 0.00% BAC after his last drink. Women and lighter individuals will generally take longer.

These estimates assume drinks consumed over about an hour with no food. Spread those same drinks over several hours and your BAC will peak lower and clear faster. The calculator above factors in drinking duration, so use it if you want something more tailored to your situation.

Weight is one of the biggest factors. Alcohol distributes through the water in your body, so a larger person has more total fluid volume for it to spread through. A 120-pound person drinking two beers will hit a noticeably higher BAC than a 220-pound person drinking the exact same two beers.

This also means your relationship with alcohol shifts when your weight changes. A 40-pound weight gain genuinely affects how your body processes alcohol. It's not just about tolerance from regular drinking.

As covered in the formula section, women typically reach higher BAC levels than men of the same weight drinking the same amount. Body composition is part of it, more fat and less water-absorbing muscle tissue. But there's another piece: women have lower levels of alcohol dehydrogenase (ADH), the enzyme that starts breaking down alcohol in the stomach before it even hits the bloodstream.

That means more alcohol gets absorbed and less gets metabolized on the way in. Practically speaking, women are more vulnerable to alcohol's effects at lower doses, and the health risks from heavy drinking add up faster over time.

Eating before or while drinking is one of the most effective ways to keep your BAC in check. Food in your stomach slows how quickly alcohol passes through the pyloric valve into the small intestine, which is where most absorption happens. A solid meal before drinking can noticeably cut your peak BAC compared to drinking on an empty stomach.

Drinking speed matters just as much. Slamming three drinks in 30 minutes spikes your BAC fast. Spread those same three drinks over three hours and your liver has time to process the alcohol as you go, keeping your peak much lower.

Medications are a wildcard. Some prescription and over-the-counter drugs interact with alcohol in ways that amplify its effects or change how quickly your body processes it. Antihistamines, benzodiazepines, opioids, and certain antidepressants can all intensify impairment at BAC levels that would otherwise feel manageable. If you're on any medication, it's worth checking with your pharmacist before drinking, even casually.