BAC Calculator

The calculator uses the Widmark formula. It takes the amount of pure alcohol you drank, your body weight, your biological sex, and the time since your first drink. It then estimates how much alcohol is still in your blood. The formula accounts for body water differences between males and females and assumes your body removes about 0.015% BAC per hour.

The Widmark formula is: BAC = (alcohol in ounces × 5.14) ÷ (body weight in pounds × r factor) − 0.015 × hours. The r factor is 0.73 for males and 0.66 for females. This formula has been used since the 1930s and is still the standard method for estimating BAC.

This calculator gives a rough estimate. Real BAC depends on many things the formula cannot measure, such as how much food you ate, your metabolism, your health, and any medications you take. A certified breathalyzer or blood test is the only way to know your true BAC. Never use this tool to decide if you are safe to drive.

ABV stands for alcohol by volume. It is the percentage of pure alcohol in a drink. A beer labeled 5% ABV means 5% of the liquid is pure alcohol. Higher ABV means a stronger drink. You can usually find the ABV on the bottle or can label.

Male and female bodies hold different amounts of water on average. Since alcohol spreads through body water, females typically reach a higher BAC than males after drinking the same amount. The calculator uses an r factor of 0.73 for males and 0.66 for females to account for this difference.

A heavier person has more body water for alcohol to spread into. This means the same number of drinks produces a lower BAC in a heavier person and a higher BAC in a lighter person. That is why weight is a key part of the formula.

Your liver breaks down alcohol at a fairly steady rate. On average, your BAC drops by about 0.015% every hour. This rate is roughly the same for most people and cannot be sped up by drinking water, eating food, or sleeping.

You can, but the result will be less accurate. The Widmark formula works best when you enter all the drinks you plan to have and the full time since your first drink. If you are still drinking, your BAC is likely still rising, and the estimate may not reflect your peak level.

Elapsed duration lets you type in how many hours and minutes have passed since your first drink. Clock time lets you enter the actual time you started drinking, and the calculator figures out the elapsed time for you. Both give the same result — just pick whichever is easier for you.

Use the Custom Creator tab. Enter the drink name, volume, volume unit, ABV percentage, and quantity. Then press the plus button to add it to your drink log. You can also use the "Other" row in the Standard Table and type in any size and ABV.

If you know how many standard drinks you had but do not remember the exact sizes or ABV, type that number in the Standard Drink Units field. The calculator treats each unit as 0.6 fluid ounces of pure alcohol, which is one U.S. standard drink (about 14 grams).

The gauge is a color bar that shows your estimated BAC on a scale from 0.00% to 0.40%+. Green means low risk, yellow means caution, orange means impaired, and red means severe danger. A black pointer marks where your estimated BAC falls on the scale.

The chart draws a line that starts at your current estimated BAC and slopes down to 0.00% over time. It also shows horizontal lines for legal limits in your area. This helps you see roughly how many hours it may take for your BAC to drop below the legal limit and reach zero.

The calculator divides your current estimated BAC by 0.015 (the average hourly drop rate). For example, if your BAC is 0.060%, it would take about 0.060 ÷ 0.015 = 4 hours to reach 0.00%. This is an estimate and may vary from person to person.

It compares your total drinks to the U.S. NIAAA weekly guideline: no more than 14 standard drinks per week for males and 7 per week for females. The bar shows what percentage of that weekly limit your current session represents. It is for information only.

Eating food before or while drinking can slow down how fast alcohol enters your blood, which may result in a lower peak BAC. However, eating after you are already drunk does not remove alcohol from your system. Only time lowers your BAC once the alcohol is absorbed.

No. Coffee may make you feel more alert, but it does not lower your BAC. Water helps prevent dehydration but does not speed up alcohol processing. Your liver works at a fixed rate of about 0.015% per hour no matter what you eat or drink.

Each country and jurisdiction sets its own legal BAC driving limits. For example, most U.S. states use 0.08%, Utah uses 0.05%, and Scotland uses 0.05%. When you change the country or region, the calculator loads the correct limits and updates the legal reference table and countdown timer.

Zero tolerance is a very low or 0.00% BAC limit, usually applied to drivers under 21. Enhanced penalty is a higher BAC threshold, often around 0.15% or 0.16%, where punishments become much more severe, such as longer license suspensions or mandatory jail time.

Yes. Use the weight unit dropdown next to the weight field. When you switch units, the calculator automatically converts your weight so you do not have to re-enter it. If you choose stones, a second field appears for the remaining pounds.

You can enter drink volume in milliliters (ml), liters (L), US fluid ounces, US cups, US pints, UK fluid ounces, UK pints, or metric cups. The calculator converts everything to fluid ounces internally before running the formula.

A BAC of 0.00% means no measurable alcohol in your blood. However, this calculator only provides an estimate. You may still feel tired or unwell from drinking even after your BAC returns to zero. Always make sure you feel fully alert and capable before driving.

If someone shows signs of alcohol poisoning — such as slow or irregular breathing, pale or blue skin, vomiting while unconscious, or being unable to wake up — call emergency services right away. Do not leave them alone. Lay them on their side to prevent choking. A BAC above 0.30% is a medical emergency.

No. All calculations happen in your web browser. Nothing you enter is sent to a server or saved anywhere. When you close or refresh the page, all your inputs and results are gone.

This usually means enough time has passed for your body to fully process the alcohol. If the elapsed time you entered is long enough, the formula will return 0.000%. Check that your time entry is correct. Also make sure your weight is entered properly, since a very high weight with few drinks can produce a near-zero result.