BAC (Blood Alcohol Content) Calculator
Health & FitnessEstimate your blood alcohol content (BAC), time until sober, and time until under the legal limit, using the Widmark formula.
Estimated BAC
Estimated blood alcohol content as a percentage, using the Widmark formula. This is an approximation only. Never use it to judge whether it is safe to drive.
Time Until Sober
3h 9m
Estimated hours and minutes from now until your BAC returns to 0%, based on the same average elimination rate.
Time Until Under 0.08%
Already under 0.08%
Estimated time from now until your BAC drops under the standard 0.08% US legal driving limit. This is not the same as being safe to drive.
Estimated Impairment Level
A general effects classification for your current estimated BAC, based on published NHTSA and clinical reference ranges. Mild relaxation and slight impairment
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Odeh AhwalBased on 3 sources
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SponsoredBlood alcohol content, or BAC, measures how much alcohol is in your bloodstream at a given moment, expressed as a percentage. This calculator estimates your BAC using the Widmark formula, a well established method that combines your body weight, biological sex, the number of standard drinks you have had, and the time since you started drinking.
Beyond a single BAC estimate, this tool also tells you roughly how long it will take for your body to eliminate the alcohol completely, and separately, how long until your estimated BAC drops back under the standard 0.08% legal driving limit used in most US states. Both figures update automatically from the same inputs you already entered.
Like every BAC calculator, this is an estimate, not a measurement. The Widmark formula assumes an average elimination rate and a fixed distribution of alcohol through body water based on sex alone. Real BAC varies with genetics, medication, liver function, and especially whether you have eaten, none of which this or any other formula based calculator can fully account for. Some published sources use a slightly different elimination rate constant, commonly between 0.015% and 0.017% per hour. This tool uses 0.015%, a widely cited average. The Widmark formula also splits its distribution ratio by sex assigned at birth only, since no separately validated version of the formula exists yet for transgender or non-binary people. That is a real limitation of the underlying science, not something specific to this calculator.
Use this calculator to understand roughly where you stand after drinking, not to decide whether it is safe to drive. The only way to know your actual BAC is a breathalyzer or blood test, and the only way to be certain you are safe to drive is to wait it out or arrange another ride.
How Long Until You Are Sober
One of the most common questions after drinking is simply how long alcohol takes to leave your system completely. This calculator answers that directly: using the same weight, drinks, and time inputs entered above, it estimates the number of hours remaining until your BAC returns to 0%, shown as the Time Until Sober result.
As a rough guide, the body eliminates roughly one standard drink worth of alcohol per hour on average, though this varies by individual. If you are tracking a longer stretch of sobriety rather than a single night of drinking, the Sobriety Calculator counts days, not hours.
This estimate only accounts for alcohol already in your system based on what you entered. If you continue drinking after using this calculator, the real time until sober will be longer than what is shown here.
Understanding Your BAC Level
Blood alcohol content does not affect everyone the same way at the same number, but public health agencies publish general effect ranges based on population data. The table below, based on data published by the National Highway Traffic Safety Administration (NHTSA), shows typical effects at each BAC range.
| BAC | Typical Effects |
|---|---|
| 0.02% | Slight body warmth, relaxed mood, some loss of judgment |
| 0.05% | Exaggerated behavior, reduced coordination, impaired judgment |
| 0.08% | Poor muscle coordination, impaired reasoning and memory (the standard US legal limit) |
| 0.10% | Clear loss of balance and reaction time, slurred speech |
| 0.15% | Major loss of balance, possible vomiting, substantial impairment |
Some lab reports and international sources give blood alcohol as milligrams per deciliter (mg/dL) or per mille (parts per thousand, written per-mille) instead of a direct percentage. The conversion is straightforward: 0.08% is the same concentration as 80 mg/dL and the same as 0.8 per mille, just three different ways of writing the identical number.
Dangerous and Lethal BAC Levels
NHTSA's published table stops at 0.15%, but BAC can climb much higher. Medical sources generally agree that levels above 0.30% risk loss of consciousness, and levels above 0.40% carry a real risk of death from alcohol poisoning, including suppressed breathing and heart rate. The highest confirmed blood alcohol level a person has survived is reported at around 1.5%, an extreme medical outlier, not a safe reference point of any kind.
Legal BAC Limits for Driving in the US
The legal limit to drive in the United States is 0.08% BAC in every state except Utah, where it is 0.05%. Lower limits apply to two groups of drivers, listed in the table below.
| Driver Type | Legal BAC Limit |
|---|---|
| Standard driver (21+) | 0.08% (0.05% in Utah) |
| Commercial driver (CDL) | 0.04% |
| Driver under 21 | Zero tolerance, typically 0.00% to 0.02% depending on state |
These are legal thresholds for driving specifically, not a safety guarantee. Judgment and coordination measurably decline well below 0.08%, so the Time Until Legal result above should never be read as a Time Until Safe result.
What Counts as a Standard Drink
This calculator assumes each drink entered contains 14 grams of pure alcohol, the standard US definition. That is roughly a 12 oz beer at 5% ABV, a 5 oz glass of wine at 12% ABV, or a 1.5 oz shot of spirits at 40% ABV. If you think in UK style alcohol units instead of US standard drinks, the Alcohol Units Calculator converts between them.
Want the standard drink math on its own, without a BAC estimate attached? The Standard Drink Calculator breaks a specific drink down by size and ABV directly.
Frequently Asked Questions
How accurate is this BAC calculator?
The Widmark formula used here gives a rough estimate only. Actual BAC depends on metabolism, food intake, medication, liver function, and drink strength, none of which a formula based calculator can measure directly. Never use this result to judge whether it is safe to drive.
What counts as one standard drink?
One standard drink is defined as 14 grams of pure alcohol in the US, roughly a 12 oz beer at 5% ABV, a 5 oz glass of wine at 12% ABV, or a 1.5 oz shot of spirits at 40% ABV.
How fast does the body eliminate alcohol?
On average, the body eliminates about 0.015% BAC per hour, the rate this calculator uses. Published sources vary somewhat, commonly citing a range between 0.015% and 0.017% per hour depending on individual metabolism, so treat any single number as an average, not a guarantee.
How long does alcohol stay in your system?
Total elimination time depends on how much you drank and how much time has already passed, which is exactly what the Time Until Sober result above calculates from your own inputs. As a rough rule of thumb, the body processes roughly one standard drink per hour, so a night of heavy drinking can take many hours to fully clear even after you stop.
What BAC is considered legally drunk for driving?
In the United States, 0.08% BAC is the legal limit to drive in every state except Utah, where it is 0.05%. Commercial drivers face a lower 0.04% limit, and every state enforces a zero tolerance policy for drivers under 21, typically 0.02% or lower.
Does food affect your BAC?
Yes. Drinking on an empty stomach lets alcohol reach your bloodstream faster, producing a higher peak BAC than the same drinks consumed with food. This calculator does not have a food input, so treat its estimate as a baseline that could run higher if you drank quickly on an empty stomach.
What is considered a dangerous or lethal BAC level?
Effects become severe above roughly 0.30%, with real risk of loss of consciousness, and levels above 0.40% carry a genuine risk of death from suppressed breathing and heart rate. Anyone showing signs of alcohol poisoning, such as vomiting while unconscious, slow or irregular breathing, or unresponsiveness, needs emergency medical help immediately, not a calculator.
Can I use this calculator to decide if it is safe to drive?
No. This tool gives an educational estimate only. The only reliable way to know your actual BAC is a breathalyzer or blood test, and the only way to be certain you are safe to drive is to wait well beyond the estimated Time Until Legal result or arrange another ride.
Why do different BAC calculators give slightly different results?
Every BAC calculator relies on the same basic Widmark formula, but sources differ slightly on the average elimination rate and the exact body water distribution ratio used for each sex. These small differences in assumptions, not a bug, explain why two calculators can give slightly different numbers from the same inputs.
How many drinks does it take to reach 0.08% BAC?
It depends heavily on body weight and sex, which is why this calculator asks for those inputs rather than giving one fixed number. As a rough average reference point only, a 180 lb (82 kg) man typically reaches around 0.08% after about 4 standard drinks in an hour, and a 140 lb (64 kg) woman after about 2 to 3. Enter your own weight, sex, and drink count above for a real estimate rather than relying on this average.
Sources
- Drunk Driving: Statistics and Resources, National Highway Traffic Safety Administration (NHTSA)
- Driver Disqualification for Blood Alcohol Concentration, Federal Motor Carrier Safety Administration (FMCSA)
- Vital Signs: Teen Drinking and Driving, Centers for Disease Control and Prevention (CDC)
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