Alcohol Units / BAC Rough Estimator (Educational Only)

You had two glasses of wine at dinner and want a rough idea of where your blood alcohol concentration might land. A BAC estimator plugs your drinks, body weight, and sex into a formula and spits out a number. A common mistake is treating that number as gospel. It is not. Real BAC depends on dozens of factors the formula cannot capture: what you ate, how fast you drank, your metabolism, medications, and more. The estimate gives you a ballpark, nothing more.

This calculator converts your drinks into standard units first. In the US, one standard unit contains about 14 grams of pure alcohol, roughly what you get in 12 ounces of regular beer, 5 ounces of wine, or 1.5 ounces of spirits. Once total grams are known, the formula estimates peak BAC using your weight and a body water factor. It also subtracts elimination over time at roughly 0.015 percent per hour.

Keep in mind that individual variation is huge. Two people of the same weight can end up with noticeably different BAC after the same drinks. The calculator is for educational awareness, not for deciding whether you are fit to do anything.

A pint glass at a pub holds 16 ounces, not 12. A generous restaurant pour of wine often tops 6 ounces. A craft IPA might clock in at 7 or 8 percent alcohol instead of the usual 5. These differences add up fast. What looks like two drinks on paper might actually deliver three or four standard units.

The calculator asks for volume and ABV (alcohol by volume) so it can compute grams precisely. If you just say "two beers," the result assumes 12 ounces at 5 percent. If your beers were 16-ounce pints of a 7-percent IPA, the actual alcohol content is nearly double. Accuracy matters if you want a meaningful estimate.

Cocktails are especially tricky. A margarita might contain 2 ounces of tequila, half an ounce of triple sec, and lime juice. The tequila alone is 1.3 standard units. Add the triple sec and you are pushing 1.5 units per drink. A Long Island Iced Tea can pack four or five units into a single glass. Know what you are drinking, or the estimate will be way off.

Common scenario: A 70-kilogram man has two 12-ounce beers at 5 percent ABV over two hours. Total alcohol is about 28 grams, or 2 standard units. Using a body water factor of 0.68 for males, peak BAC estimates at roughly 0.059 percent. After two hours of elimination at 0.015 percent per hour, current BAC sits around 0.029 percent. He feels mildly relaxed but not impaired. The estimate matches his subjective sense.

Edge case: A 55-kilogram woman has one 9-ounce glass of wine at 14 percent ABV and one 2-ounce pour of whiskey at 40 percent ABV over 90 minutes. The wine alone is about 30 grams; the whiskey adds another 19 grams. Total is 49 grams, roughly 3.5 standard units. Using a body water factor of 0.55 for females, peak BAC estimates at around 0.16 percent, which is high. After 90 minutes of elimination, current BAC is still above 0.13 percent. She feels noticeably impaired, and the estimate confirms why.

These examples show how drink type, volume, and ABV all shape the final number. The calculator handles the math; you need to enter accurate inputs.

Body weight matters because alcohol distributes through body water. A heavier person has more water to dilute the alcohol, so BAC tends to be lower. Sex matters because females typically have a higher body fat percentage and less body water than males of the same weight, leading to higher BAC for the same dose.

Food slows absorption. Drinking on an empty stomach lets alcohol hit your bloodstream faster, producing a sharper peak. A full meal can delay and flatten the curve. The calculator does not ask about food, so it assumes a moderate stomach state. Your actual peak could be higher or lower depending on what you ate.

Metabolism varies too. Some people clear alcohol faster than others due to enzyme differences. Medications can slow elimination or amplify impairment even at lower BAC. Age, liver health, hydration, and even fatigue all play roles. The formula uses average constants, but you are not average in every respect.

This calculator cannot tell you whether you are safe to drive. It cannot predict what a breathalyzer would read. It cannot account for impairment that occurs even at low BAC levels. If you have consumed any alcohol and need to go somewhere, the only safe choice is to use a designated driver, rideshare, taxi, or public transit.

Legal limits in most US states sit at 0.08 percent BAC for adults over 21, but impairment starts well before that threshold. Reaction time, judgment, and coordination degrade at 0.02 or 0.03 percent, levels that feel barely noticeable. The law sets a line; biology does not care about the line.

Never treat a BAC estimate as permission to operate a vehicle, machinery, or anything else that requires full attention. The estimate is educational. The consequences of getting it wrong are not.

This calculator uses the Widmark formula, a classic method for estimating BAC from alcohol consumed, body weight, and body water distribution. Standard drink definitions follow the NIAAA guideline of 14 grams of pure alcohol per unit. Elimination rates follow commonly cited averages of 0.015 to 0.017 percent per hour.

• NIAAA: National Institute on Alcohol Abuse and Alcoholism
• CDC: Alcohol and Public Health
• NHTSA: Drunk Driving Information

Critical warning: This calculator is for educational purposes only and does not provide medical, legal, or safety advice. BAC estimates are rough approximations that cannot account for individual variation, food intake, medications, or other factors. Never use any BAC calculator to decide whether you are safe or legal to drive, operate machinery, or perform any activity requiring alertness. If you have consumed alcohol, arrange safe transportation. If you have concerns about alcohol use, contact SAMHSA's National Helpline at 1-800-662-4357.