Estimate your blood alcohol concentration using the Widmark formula — understand how weight, sex, and drink count affect BAC, standard drink sizes, and alcohol metabolism rates.
Amount of Alcohol Consumed
| Type | Amount | Size | ABV |
|---|---|---|---|
| 🍺 Beer | ml | % | |
| 🍷 Wine | ml | % | |
| 🥃 Liquor | ml | % | |
| 🍸 Other | ml | % |
The BAC Calculator is built for adults who want to understand how their body processes alcohol and where they might fall on the BAC scale after a given number of drinks. You enter your body weight, biological sex, the number of standard drinks consumed, and the hours elapsed since you started drinking. The tool applies the Widmark formula — the clinical standard used in alcohol pharmacokinetics research — to return an estimated BAC percentage. Results reflect an estimate based on population averages; individual metabolism, food intake, medications, health status, and tolerance all affect actual BAC. The calculator is appropriate for educational contexts: understanding the math behind BAC, seeing how weight and sex affect alcohol processing, and learning how long it typically takes to metabolize alcohol. It is not appropriate for making driving decisions.
Enter your body weight (pounds or kg), biological sex, the number of standard drinks consumed, and how many hours have passed since your first drink, then tap calculate. The result is an estimated BAC percentage. A BAC of 0.02%–0.03% is mild relaxation for most people; 0.05% brings measurable impairment in coordination and judgment; 0.08% is the US federal legal driving limit; 0.10%–0.15% brings significant impairment; above 0.25% is in the dangerous-to-life-threatening range, per CDC guidance on alcohol impairment effects. Remember: your personal impairment may differ from the estimate. Food, sleep deprivation, medications, and individual metabolism all shift the curve. Never use this number to make a driving decision.
The BAC Calculator uses the Widmark formula, the standard pharmacokinetic model for alcohol estimation:
BAC = (Drinks × 14g of pure alcohol) ÷ (Body Weight (g) × r) − (Metabolism Rate × Hours)
14g = grams of pure alcohol in one NIAAA standard drink
r = body water distribution constant (0.73 for males, 0.66 for females)
Metabolism Rate ≈ 0.015% per hour (average)
The r factor reflects that women typically have lower body water content, leading to higher BAC per drink at the same weight.
Most people significantly underestimate how much alcohol is in what they're drinking, which is why "standard drink" is one of the most important concepts in any BAC discussion. The NIAAA defines one standard drink as containing 14 grams (0.6 fluid ounces) of pure ethanol. That translates to: 12 oz of regular beer at ~5% ABV, 5 oz of wine at ~12% ABV, or 1.5 oz of 80-proof distilled spirits at 40% ABV. The trap is that many drinks pour larger than a standard drink. A restaurant pour of wine is often 6–8 oz, not 5. A craft beer at 8% ABV in a 16-oz glass contains roughly 2.7 standard drinks. A "double" cocktail can equal three standard drinks. When using this calculator, count actual standard drinks by ABV and volume — not glasses. Overestimating the number of standard drinks will produce an overestimated BAC; underestimating is the more common and more dangerous error.
The degree of impairment caused by alcohol intoxication varies based on BAC, as shown in the table below. Impairments range from subtle effects at levels between 0.001–0.029%, to a serious possibility of death at 0.50% or more.
| BAC (%) | Behavior | Impairment |
|---|---|---|
| 0.001–0.029 | Subtle effects detected with specialized tests; appears normal | Attention, divided attention, and tracking slightly impaired |
| 0.030–0.059 | Mild euphoria, relaxation, talkativeness, decreased inhibition | Alertness, judgment, coordination, and concentration mildly impaired |
| 0.060–0.099 | Blunted feelings, disinhibition, extroversion, impaired reasoning | Reflexes, reasoning, depth perception, and peripheral vision impaired |
| 0.100–0.199 | Over-expression, emotional swings, anger, loudness, loss of balance | Gross motor control, slurred speech, reaction time significantly impaired |
| 0.200–0.299 | Stupor, confusion, dizziness, blackouts, vomiting | Severe motor impairment, loss of consciousness, memory blackout |
| 0.300–0.399 | Unconsciousness, depressed or absent reflexes, hypothermia | Potential for life-threatening respiratory depression |
| 0.400–0.500+ | Complete unconsciousness, coma, possible death | Respiratory arrest, death possible at 0.50% and above |
Understanding what a given BAC actually does to your body helps put the numbers in context. The CDC documents a consistent progression of impairment with rising BAC:
This is one of the most frequently searched alcohol questions, and the answer comes down to a fairly consistent metabolic rate. The liver processes alcohol at approximately 0.015% BAC per hour for most adults — equivalent to roughly one standard drink per hour, per NIAAA pharmacokinetics data. Nothing speeds up this process: not food, not coffee, not water, not sleep. Once alcohol is in your bloodstream, your liver works at a fixed enzymatic rate. What food, water, and sleep do is help you feel better — they do not change BAC clearance speed. To estimate how long until your BAC returns to zero: divide your peak estimated BAC by 0.015 to get the approximate number of hours. A peak BAC of 0.09% would take approximately six hours to reach zero at the average metabolism rate (0.09 ÷ 0.015 = 6 hours). Individual variation around this average can be ±30%.
The US federal baseline for DUI/DWI is 0.08% BAC for drivers 21 and older. All 50 states have adopted this as their standard legal limit under National Highway Traffic Safety Administration (NHTSA) pressure tied to federal highway funding. The one exception is Utah, which lowered its limit to 0.05% in 2018 — the strictest in the nation. Zero-tolerance laws apply for drivers under 21 in all states: any detectable BAC (typically 0.01%–0.02%) constitutes a DUI offense for minors. Commercial drivers face a 0.04% limit in all states. Many states also have "enhanced penalty" thresholds (often 0.16% or 0.20%) that carry steeper fines and longer license suspensions. A BAC at or below the legal limit doesn't mean driving is safe — impairment begins well below 0.08%, as the CDC notes. The legal limit is not a safety threshold; it is a criminal prosecution threshold. Do not drive after drinking.
Important: A person should not begin drinking for potential health benefits. Those who already drink light to moderate amounts can probably continue drinking moderately. Most importantly, consult your doctor regarding alcohol consumption to determine what is safe for your particular situation.
The Widmark formula is useful for education and average-population estimates, but several factors create real-world inaccuracy in individual cases. Food in the stomach slows alcohol absorption significantly — someone who ate a full meal before drinking may have a peak BAC 30–50% lower than the formula predicts because food delays gastric emptying into the small intestine, where most absorption occurs. Carbonated beverages (champagne, cocktails with soda) accelerate absorption. Medications — including antihistamines, anxiolytics, and antibiotics — interact with alcohol metabolism unpredictably. Liver disease reduces the metabolic rate. And alcohol tolerance, while not changing actual BAC, changes the perception of impairment: a regular heavy drinker may feel unimpaired at 0.12% while a light drinker feels significantly impaired at 0.06%. This calculator gives a population average; your actual BAC and your actual impairment may differ meaningfully. That's exactly why it must never be used to make driving decisions.
Alcohol consumption has a number of short-term, as well as long-term effects. Short-term effects include dehydration and intoxication, while more long-term effects can include changes in the metabolism of the liver and brain. Alcohol consumption can also result in alcoholism, which is generally described as the use of alcohol that results in problems with mental or physical health.
Body weight is the dominant input: heavier individuals distribute the same amount of alcohol over more body water, resulting in lower BAC per drink. Biological sex is the second key factor — the r constant (0.66 for females, 0.73 for males) reflects body water percentage differences, meaning women typically reach higher BAC than men of the same weight after the same number of drinks. Time elapsed allows the formula to subtract the alcohol already metabolized (at ~0.015%/hour). Number of standard drinks is the most commonly miscounted input, as discussed above — ABV and pour size both matter. Factors the formula cannot capture: food consumption, individual metabolism variation (genetics affect ADH and ALDH enzyme levels), medications, and health conditions.
Jordan consumed four standard drinks over two hours at a birthday party. Formula: (4 × 14) ÷ (175 × 453.6 × 0.73) × 100 − (0.015 × 2) ≈ 0.086%. Jordan's estimated BAC is approximately 0.086% — above the legal limit. He calls a rideshare. Two hours later, his estimated BAC would be approximately 0.086 − (0.015 × 2) = 0.056% — below the legal limit but still carrying measurable impairment.
Maya had three standard drinks over 1.5 hours at a dinner. Formula: (3 × 14) ÷ (130 × 453.6 × 0.66) × 100 − (0.015 × 1.5) ≈ 0.097%. Her estimated BAC is approximately 0.097% — above the legal limit in all US states. The same three drinks that might leave a 180-pound man at 0.06% put her well over 0.08%. Body weight and the sex-based r factor are why the same number of drinks produces very different results for different people.
Count standard drinks by ABV and actual pour size, not by glass count — a 9% ABV beer in a 16-oz pint counts as about 2.4 standard drinks.
Remember that the liver processes alcohol at approximately 0.015% BAC per hour regardless of what you eat or drink after the fact.
If you're unsure whether you're below the legal limit, you are almost certainly in no position to make that judgment accurately — impaired judgment is one of the first effects of alcohol.
Plan ahead: arrange a designated driver or rideshare before you start drinking, not after.
Never use this calculator to justify driving. It is an estimate; there is no safe-to-drive calculation. Do not drive after drinking.
Use this tool to understand how body weight, sex, and drink count interact with BAC — not as a real-time sobriety test.
The legal limit for driving is 0.08% BAC in all US states except Utah, which is 0.05%, per NIAAA. For drivers under 21, zero-tolerance laws apply — any detectable BAC constitutes a violation in all states.
It depends on body weight, sex, and time. A 130-pound woman typically reaches 0.08% after roughly two to three standard drinks in an hour; a 200-pound man might take four to five. Use the calculator with your actual stats — averages are misleading.
Divide your peak estimated BAC by 0.015 (the average hourly metabolism rate) to get the approximate hours to zero. A peak of 0.09% takes about six hours to clear. Nothing speeds this up — not coffee, food, or water, per NIAAA data.
NIAAA defines one standard drink as containing 14 grams of pure ethanol — equivalent to 12 oz of regular beer (~5% ABV), 5 oz of wine (~12% ABV), or 1.5 oz of 80-proof spirits.
The Widmark r factor differs by sex (0.73 for males, 0.66 for females) because women typically have a higher proportion of body fat and lower total body water. Since alcohol distributes in water rather than fat, the same drink produces higher BAC in a woman than in a man of the same weight.
No. Impairment begins well below the legal limit, and the CDC documents measurable driving impairment at 0.05%. The calculator also produces an estimate — individual factors can make your actual BAC and impairment higher than the formula shows. Do not drive after drinking.
The Widmark formula provides a population average estimate. Individual results vary significantly based on food intake, metabolism, medications, and genetics. Treat the result as an educational approximation, not a precise measurement.
Brief disclaimer: This calculator provides educational BAC estimates using the Widmark formula. Results are population-average approximations and do not reflect individual metabolism, food intake, medications, health conditions, or tolerance. This tool must never be used to determine whether it is safe to drive. Do not drive after drinking. If you believe you have an alcohol use disorder or are concerned about your drinking, contact a healthcare provider or the SAMHSA National Helpline at 1-800-662-4357.