Estimate blood alcohol content using the Widmark formula from your gender, body weight, number of standard drinks, and hours elapsed. Educational estimate only — never use this tool to decide whether it's safe to drive.
🥃 One US standard drink ≈ 0.6 fl oz of pure alcohol — 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 all count as roughly one standard drink. Large pours, craft beers, and mixed cocktails often contain more than one.
This is a rough educational estimate only. Actual BAC is affected by many factors this formula cannot capture (food intake, medication, individual metabolism, liver function, drink strength, hydration, and more) and can be meaningfully higher or lower than shown here. Never use this tool to decide whether it is safe to drive or operate machinery. If you've been drinking, do not drive — use a taxi, rideshare, public transit, or a designated driver. If you or someone else shows signs of alcohol poisoning (confusion, vomiting, seizures, slow/irregular breathing, bluish skin, unconsciousness), call emergency services immediately.
📋 Reference only — not driving guidance: the typical US legal limit is 0.08% BAC for most drivers 21+, 0.02% for drivers under 21 in zero-tolerance states, and 0.04% for commercial drivers. Some other countries use limits as low as 0.02–0.05%. This calculator cannot tell you whether you are legally or actually safe to drive.
Enter your details to estimate blood alcohol content
This is a rough educational estimate only. Actual blood alcohol content is affected by many factors this formula cannot capture, including food intake, medication, individual metabolism, liver function, the real strength of your drinks, hydration, and more. Your true BAC can be meaningfully higher or lower than the number this calculator produces.
Never use this tool to decide whether it is safe to drive or operate machinery. If you have been drinking, do not drive — use a taxi, rideshare, public transit, or a designated driver instead. There is no BAC number, calculator, or personal breathalyzer that can reliably certify you are safe behind the wheel.
If you or someone else shows signs of alcohol poisoning — confusion, vomiting, seizures, slow or irregular breathing, bluish or pale skin, or unconsciousness — call emergency services immediately. This tool provides no legal or medical guarantee of any kind.
This BAC calculator provides a rough educational estimate only — it cannot measure your actual blood alcohol content and should never be used to decide whether it is safe to drive or operate machinery. Blood alcohol content (BAC) is the percentage of alcohol present in a person's bloodstream, expressed as grams of alcohol per 100 milliliters of blood. This calculator uses the Widmark equation, a formula developed in the 1930s that's still widely referenced today, to approximate BAC from your gender, body weight, number of standard drinks, and hours elapsed since your first drink. Because the formula relies on population averages rather than your individual physiology, its estimate is inherently limited — real BAC depends on factors like food intake, medication, liver function, hydration, and genuine drink strength that no simple equation can fully capture.
The calculator estimates your current BAC percentage by approximating how much alcohol has entered your bloodstream relative to your body's water content, then subtracting the amount your liver has likely already metabolized based on time elapsed. It also projects roughly how many more hours it would take for that estimated BAC to reach 0.00% at an average elimination rate, plus what clock time that would be.
This tool is intended for adults who want a general, educational sense of how drinks, body weight, gender, and time interact to affect blood alcohol levels — for example, when planning a night out, hosting an event, or simply learning how alcohol metabolism works. It is not intended for anyone under the legal drinking age, and it is not a substitute for a certified breathalyzer, blood test, or professional medical or legal judgment in any situation.
Many people significantly underestimate how much alcohol they've actually consumed or how long it takes for that alcohol to clear their system — a single "drink" at a bar or party can easily contain more alcohol than a standard measure. Understanding the rough scale of the Widmark formula, and just as importantly its limitations, can support better harm-reduction planning, such as arranging a ride home in advance or pacing drinks at a social event, without ever substituting for professional or legal certainty about impairment.
Exactly how this calculator converts drinks, weight, gender, and time into an estimated BAC
If entering weight in kilograms, the calculator first converts to pounds (kg × 2.20462) before applying the formula. The result is floored at 0% — a negative result simply means the alcohol has likely been fully metabolized by the time entered, and is displayed as "0.00% — Alcohol likely fully metabolized" rather than a negative number.
Every drink is converted to a common unit: 0.6 fl oz of pure alcohol. A beer, glass of wine, and shot of spirits are designed to each contain roughly one standard drink, even though their volumes differ enormously, because their alcohol percentages differ too.
This factor approximates the share of body weight that is water, since alcohol distributes through body water rather than fat. Men use r = 0.73 and women use r = 0.66 on average, reflecting typical differences in body composition — not a judgment about any individual.
The liver metabolizes alcohol at a roughly steady average rate, commonly cited as about 0.015% BAC per hour. This calculator subtracts that rate multiplied by hours elapsed to approximate how much alcohol your body has already processed.
From entering your details to reading your estimated BAC and time-to-sober projection
Gender determines the Widmark factor (r) used in the formula — 0.73 for men and 0.66 for women, reflecting average differences in body water composition.
Choose Metric (kg) or Imperial (lbs) and enter your current body weight. Kilograms are converted to pounds internally before the formula is applied.
Count each beer, glass of wine, or shot of spirits as roughly one standard drink. Larger pours, craft beers, and mixed cocktails often count as more than one.
This is used to subtract the alcohol your body has likely already metabolized, at an average rate of about 0.015% per hour.
See your estimated BAC, a color-coded impairment-level badge, estimated hours and clock time until 0.00%, and a projected decline chart. Read the safety disclaimer carefully — this is an educational estimate only.
A 180 lb man, 4 standard drinks, 2 hours since the first drink
A man weighing 180 lbs has consumed 4 standard drinks over the course of an evening, and 2 hours have passed since his first drink.
Explanation: At an estimated 0.06%, this falls in the "Mild Impairment" range on this calculator's scale — below the common 0.08% legal driving limit referenced for most US states, but this number is a rough estimate, not a legal or medical certainty, and it should never be used to decide whether driving is actually safe. A different person with the same drinks and time — different weight, gender, food intake, or metabolism — could have a meaningfully different real BAC.
General, population-level BAC impairment ranges — informational only
| BAC Range | General Level | Typical Description |
|---|---|---|
| Below 0.02% | Minimal / No Impairment | Little to no measurable impairment for most people at this level |
| 0.02% – 0.05% | Mild Impairment | Possible mild relaxation or mood changes; reaction time may begin to slow slightly |
| 0.05% – 0.08% | Noticeable Impairment | Coordination, judgment, and reaction time are commonly noticeably affected |
| 0.08% and above | Legal Impairment (most US states) | At or above the common legal driving limit for most US states — impairment is generally significant |
| 0.15% and above | Significant Risk | Substantial impairment of coordination and judgment; risk of harm increases considerably |
| 0.30% and above | Danger — Alcohol Poisoning Risk | Serious risk of alcohol poisoning; loss of consciousness and life-threatening complications are possible |
These ranges are general, population-level descriptions — not a fitness-to-drive test and not a medical diagnosis. Individual reactions to the same BAC vary enormously based on tolerance, body composition, medication, fatigue, and many other factors. A person can be significantly impaired at a BAC this table labels "mild," and impairment doesn't switch on precisely at any single threshold.
This calculator provides educational estimates only and should not be used as a substitute for professional medical advice, a certified breathalyzer or blood test, or any judgment about whether it is safe to drive, work, or operate machinery. Always err on the side of caution after drinking.
Where a rough, educational BAC estimate is genuinely useful — always framed around awareness and planning, never as permission to drive
Hosts can think ahead about food, pacing, non-alcoholic options, and safe transportation for guests before an event starts.
Use the calculator's projections to decide, before drinking begins, when and how you'll get home safely.
Students and educators can use the Widmark formula to illustrate how alcohol distributes through and clears from the body.
Get a rough sense of how quickly a given number of drinks might clear your system, to support more mindful pacing.
Parents and young adults can use the calculator as an educational starting point for discussing alcohol's effects and risks.
See how a large craft beer, a strong cocktail, or several glasses of wine can add up to far more than "a couple of drinks."
HR and safety trainers can use the calculator as a discussion aid when covering workplace alcohol policies.
Get a rough educational sense of how long it might take for alcohol to clear ahead of work, sport, or other responsibilities the next day — never as a green light.
Illustrates a classic pharmacokinetic formula (distribution and first-order-like elimination) used in health-sciences education.
See, in general educational terms, how body weight and gender inputs shift the same drink count's estimated BAC in the formula.
Use the projection as a general guide to slow down or switch to water, not as permission to keep drinking up to a target number.
Groups can use the tool ahead of time to agree on who is drinking and who is staying sober to drive everyone home.
What this BAC calculator does well, and where it absolutely cannot replace real measurement or judgment
Roughly how much of a given drink type equals one US standard drink (0.6 fl oz of pure alcohol)
| Drink Type | Typical Serving | Approx. ABV |
|---|---|---|
| Regular beer | 12 fl oz (355 ml) | ~5% |
| Malt liquor | 8–9 fl oz (240–265 ml) | ~7% |
| Table wine | 5 fl oz (150 ml) | ~12% |
| Fortified wine (sherry, port) | 3–4 fl oz (90–120 ml) | ~17–20% |
| Distilled spirits (shot) | 1.5 fl oz (45 ml) | ~40% |
📋 A large craft beer, a full glass of wine poured at home, or a mixed cocktail can easily contain 1.5–3+ standard drinks in a single serving — counting by glass or can instead of actual alcohol content is one of the most common ways people underestimate their own intake.
Summary: This BAC calculator gives you a rough, educational Widmark-formula estimate of blood alcohol content, impairment level, and time until 0.00% — a general awareness and planning tool, never a measurement of whether it's safe to drive. Plan a safe ride home before you start drinking, not after. If you're also tracking what you eat and drink, remember alcoholic beverages contribute calories too — see NeftCal's Calorie Calculator for a fuller nutritional picture.
Common questions about this BAC calculator and blood alcohol content in general
Official guidance to complement this calculator — not a substitute for licensed medical or legal advice
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