BAC Calculator — Blood Alcohol Content Estimate
A rough estimate only — never a way to decide whether to drive. There is no safe amount of alcohol before driving, your real BAC can be much higher than shown, and it can still be rising after your last drink.
Estimate your blood alcohol content (BAC) from the number of US standard drinks, your body weight, your sex, and the time since your first drink — or enter beers, wine, and shots by size and ABV. It uses the Widmark equation with the NIAAA standard drink of 14 g of pure alcohol, and charts your estimated BAC curve over time against the 0.08% and Utah 0.05% limits. A general guide for education — not a breathalyzer and not a legal defense.
A rough educational estimate from the Widmark equation — not a breathalyzer and not a legal defense. Real BAC can be much higher; after drinking, do not drive.
How the BAC estimate is worked out
The Widmark equation
The calculator uses the classic Widmark equation. It takes the grams of alcohol you have consumed — the number of US standard drinks × 14 g, per the NIAAA definition — and divides by your body weight in grams (pounds are converted internally) multiplied by a distribution factor (about 0.68 for men and 0.55 for women, because women on average carry less body water). It then subtracts the alcohol your body has already eliminated, at roughly 0.015% of BAC per hour — about one standard drink an hour. The result is your estimated blood alcohol content as a percentage, plotted as a curve over time against the 0.08% and Utah 0.05% limits.
A standard drink is often less than your pour
A US standard drink is 14 g (0.6 fl oz) of pure alcohol — a 12 oz beer at 5% ABV, a 5 oz glass of wine at 12%, or a 1.5 oz shot of 80-proof liquor. Real-world servings are frequently bigger: a 16 oz craft IPA at 7% is about 1.9 standard drinks, a generous 8 oz wine pour about 1.6, and many cocktails hold 2 or more. Switch to Standard mode to enter beers, wine, and shots by size and ABV instead of counting.
Worked example
A 170 lb man having 3 standard drinks over 2 hours: 3 × 14 g = 42 g of alcohol, giving a peak BAC of about 0.080%, less roughly 0.030% eliminated over 2 hours ≈ 0.050% — under the 0.08 limit but right at Utah's 0.05, and easily higher with a bigger pour or less time. A 140 lb woman having the same three drinks over the same two hours works out to about 0.090% — over the limit in every state. Same drinks, very different result.
This is a rough estimate only. It is not a breathalyzer, not a legal defense, and your real BAC can be much higher — and can still be rising after your last drink. After drinking, the only safe choice is not to drive — call a cab, use a rideshare app, or ride with a sober driver.
What counts as a standard drink in the US
Because the calculator works in standard drinks, counting them accurately is what makes or breaks the estimate. In the US one standard drink is 14 g (0.6 fl oz) of pure alcohol — the NIAAA definition — and that is usually smaller than the drink in your hand.
- 12 oz regular beer (5% ABV) = 1 standard drink.
- 16 oz craft IPA (7% ABV) ≈ 1.9 standard drinks.
- 12 oz malt liquor (8% ABV) ≈ 1.6 standard drinks.
- 5 oz glass of wine (12% ABV) = 1 standard drink; a generous 8 oz pour ≈ 1.6.
- 1.5 oz shot of 80-proof liquor (40%) = 1 standard drink; a double = 2.
- Cocktails like a margarita, Long Island iced tea, or martini often hold 2–3 standard drinks.
- A 750 ml bottle of wine holds about 5 standard drinks.
Poured at home, a "glass" of wine or a mixed drink is often much larger than a standard drink, so it is easy to have far more than you counted. When in doubt, round up — and remember the estimate assumes each drink is exactly what you enter.
US BAC limits, sobering up, and staying safe
The drunk-driving limits
In 49 states and the District of Columbia, driving with a BAC of 0.08% or more is illegal per se — no other proof of impairment is needed. Utah lowered its limit to 0.05% in December 2018. Commercial drivers (CDL holders) are held to 0.04% in a commercial vehicle, and every state has a zero-tolerance law for drivers under 21, typically 0.00–0.02%. You can also be arrested below these numbers if you're visibly impaired — impairment starts with the first drink. See NHTSA — Drunk Driving.
| Who | Per-se limit |
|---|---|
| Drivers 21+ — 49 states + DC | 0.08% |
| Drivers 21+ — Utah | 0.05% |
| Commercial drivers (CDL), on duty | 0.04% |
| Drivers under 21 (all states) | 0.00–0.02% (zero tolerance) |
Only time sobers you up
Your body eliminates alcohol at about 0.015% of BAC per hour — roughly one standard drink an hour — and you cannot speed it up. Coffee, energy drinks, water, food, a cold shower, and fresh air do not lower your BAC; only time does. And because alcohol keeps absorbing for 30–90 minutes, your BAC can still be rising after your last drink.
The only safe choice
This tool is for general education only. It is not a breathalyzer, it is not a legal defense, and real BAC readings are often higher than an estimate. If you have had any alcohol, plan not to drive at all — call a cab or rideshare, take transit, designate a sober driver, or stay put. About a third of US traffic deaths involve an alcohol-impaired driver; it is never worth the risk.
Morning-after BAC — why you can still be over the limit
The math of a heavy night
At about 0.015% per hour, alcohol clears far more slowly than most people assume. Stop drinking at 1 am with a BAC around 0.18% and you'd still be near 0.09% at 7 am — over the limit in every state — and wouldn't reach zero until around 1 pm. Even a moderate night ending at 0.10% at midnight leaves you around 0.02% at a 5:30 am alarm. Sleep does not speed elimination.
Food, pace, and absorption
Food in your stomach slows absorption — your peak arrives later and somewhat lower — but it does not reduce the total alcohol your body has to clear. Drinking fast, or on an empty stomach, front-loads the peak. And because absorption continues for 30–90 minutes after your last drink, the reading you'd blow right after leaving the bar can be lower than the reading half an hour down the road. That's one more reason a calculator — or "feeling fine" — is never a green light.
Planning an early drive
If you have an early shift or a morning drive, count backwards from when you need to be at roughly zero using the curve above. If the math says you'll still have alcohol on board — or if you're unsure — don't drive. Feeling alert is not the same as being sober.
❓ Frequently asked Frequently asked questions
How many drinks does it take to reach a 0.08% BAC?
It depends heavily on weight and sex. Using the Widmark formula with the US standard drink of 14 g of alcohol, each drink adds a peak of roughly 0.027% BAC for a 170 lb man and about 0.040% for a 140 lb woman. So a 170 lb man reaches a peak near 0.08% after about 3 standard drinks, while about 4 drinks spread over 2 hours leaves him around 0.077% after elimination. A 140 lb woman reaches roughly 0.08% peak after only 2 drinks, and 3 drinks over 2 hours puts her near 0.090%. A 200 lb man needs about 3.5 drinks to peak at 0.08%; a 120 lb woman fewer than 2. These are population averages — pace, food, and real-world pour sizes can push any of them higher, and impairment starts well below 0.08%.
What is a standard drink in the United States?
A US standard drink contains 14 grams (0.6 fluid ounces) of pure alcohol — the NIAAA definition. That equals a 12 oz beer at 5% ABV, a 5 oz glass of wine at about 12% ABV, or a 1.5 oz shot of 80-proof (40%) distilled spirits. Real-world servings are often larger: a 16 oz craft IPA at 7% is about 1.9 standard drinks, a generous 8 oz wine pour about 1.6, and many cocktails contain 2 or more. Because the calculator works in standard drinks, counting them accurately matters — when in doubt, assume you have had more.
What is the legal BAC limit for driving in the US?
In 49 states and the District of Columbia, driving with a BAC of 0.08% or higher is illegal per se. Utah is the exception, with a 0.05% limit. Commercial drivers are held to 0.04% while operating a commercial vehicle, and all 50 states have zero-tolerance laws for drivers under 21, typically set between 0.00% and 0.02%. You can also be arrested below the per-se limit if you are visibly impaired. A calculator estimate under any limit is not permission to drive — NHTSA's position is simple: if you have been drinking, do not drive.
Why is Utah's BAC limit 0.05%?
Utah became the first state to lower its per-se limit from 0.08% to 0.05%, effective December 30, 2018. The change followed National Transportation Safety Board recommendations, noting that impairment of driving skills begins well below 0.08%. At 0.05%, a 170 lb man could be at the limit after roughly 3 standard drinks over 2 hours — a level many drivers would not feel. If you drive in Utah, the practical margin between "a couple of drinks" and the legal limit is very thin.
How fast does BAC drop, and can I speed it up?
The body eliminates alcohol at a roughly constant rate of about 0.015% BAC per hour — close to one standard drink per hour — and nothing meaningfully speeds it up. Coffee, energy drinks, cold showers, food, water, exercise, and fresh air can make you feel more alert, but they do not lower your BAC; only time does. From 0.09% it takes about 6 hours to reach zero; from 0.15%, about 10 hours. Feeling sober is not the same as being sober.
Can I still be over the limit the next morning?
Yes, easily. At about 0.015% per hour, a heavy night takes many hours to clear. If you stop drinking at 1 am with a BAC around 0.18%, you would still be near 0.09% at 7 am — over the limit in every state — and would not reach zero until around 1 pm. Sleep does not speed elimination. If you have an early drive, count backwards from when you need to be at zero, and if there is any doubt, do not drive.
What is the BAC limit for drivers under 21?
Every state has a zero-tolerance law for drivers under the legal drinking age of 21. Depending on the state, the threshold is 0.00%, 0.01%, or 0.02% — low enough that a single drink, or in some states any measurable alcohol at all, can mean license suspension and a violation. These laws exist because drivers under 21 are involved in fatal crashes at higher rates at every BAC level. For anyone under 21, the only number that matters is zero.
What is the BAC limit for commercial drivers (CDL)?
Federal rules set a 0.04% BAC limit for commercial driver's license (CDL) holders operating a commercial motor vehicle — half the standard 0.08% limit. At 0.04%, a 170 lb man could be at the limit after roughly 1.5 drinks in quick succession. Commercial drivers also face out-of-service rules for any detectable alcohol within four hours of driving, and a violation can end a driving career. For CDL holders, the practical rule is zero alcohol before work.
Why can't a BAC calculator be exact?
The Widmark formula is a population average and cannot account for your individual metabolism, body composition, hydration, food intake, medications, health conditions, or the true strength and size of each drink. BAC can also keep rising for 30 to 90 minutes after your last drink while alcohol is still being absorbed, so a calculation made right after drinking can understate your peak. Real BAC readings often come out higher than an estimate. This tool is for general education only — it is not a breathalyzer, not a legal defense, and never a way to check whether you are safe to drive.
Where these figures come from
The method reflects the widely used Widmark model with the US (NIAAA) standard drink and US per-se driving limits. Individual results vary considerably, so treat every number as a rough educational figure rather than a measurement.
- US standard drink — 14 g (0.6 fl oz) of pure alcohol — NIAAA — What Is a Standard Drink?
- Per-se limits and impaired-driving data — 0.08% in 49 states + DC, 0.05% in Utah, zero tolerance under 21 — NHTSA — Drunk Driving.
- Commercial driver (CDL) 0.04% limit and alcohol rules — FMCSA — Drug & Alcohol Testing Program.
- Impairment effects by BAC level — CDC — Impaired Driving.
- Widmark distribution factors — approximately 0.68 for men and 0.55 for women; elimination about 0.015% BAC per hour on average.
Last checked: July 2026. This is a general educational estimate, not medical or legal advice, and not a breathalyzer reading. Real BAC can be much higher than shown. The safest choice after drinking is always not to drive.
Select the question that matches where you are right now.
The headline number is your estimated blood alcohol content as a percentage, from the Widmark equation. The breakdown compares it against the 0.08% per-se limit, Utah's 0.05%, the 0.04% CDL limit, and under-21 zero tolerance, and the chart shows the estimated curve over time.
Use it only to understand how quickly drinks add up and how slowly alcohol leaves. It is educational — it is not a signal that you are safe to drive at any reading.
It is not a breathalyzer, not a legal defense, and not medical advice. Your real BAC can be much higher — and can still be rising after your last drink. Only a police test measures it for the law.
After any drinking, plan not to drive. Call a cab or rideshare, take transit, designate a sober driver, or stay the night.
Four things move your estimated BAC the most: how many standard drinks you have had, your body weight, your sex, and the time since your first drink.
Each US standard drink adds 14 g of alcohol. Craft beers, big wine pours, and strong cocktails mean more standard drinks than you may realize, pushing BAC up fast.
Alcohol spreads through body water. A lighter person, and on average a woman, reaches a higher BAC from the same drinks.
Your body clears about 0.015% per hour, so BAC falls slowly — and can still be rising up to 90 minutes after your last drink. You can be over the limit hours later, even the next morning.
There is no trick to lower your BAC quickly — but there are simple ways to stay safe.
Decide how you are getting home before you start drinking — a cab, rideshare, transit, or a designated driver.
Track standard drinks, not glasses — a 16 oz IPA is nearly two. When unsure, assume you have had more.
Only time lowers BAC. If in any doubt the next day, do not drive — you may still be over the limit.
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