BAC Calculator

Q: What is the Widmark formula?

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.

Q: What does ABV mean?

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.

Q: What is the difference between elapsed duration and clock time?

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, so pick whichever is easier for you.

Q: How do I add a drink that is not listed?

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.

Q: How is the time until 0.00% calculated?

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.

Q: Does eating food lower my BAC?

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.

Type

Qty

Size

ABV

Beer

Wine

Liquor

Other

Your Estimated BAC

Estimated Blood Alcohol Content

0.000%

Safe / Minimal

0.00%0.08%0.20%0.30%0.40%+

BAC Timeline

Time Until BAC Reaches 0.00%

0 hr 0 min

Time Until Legal Threshold

0 hr 0 min

Standard Drinks & Weekly Guideline

Informational only — based on U.S. NIAAA guidelines (14 drinks/week male, 7/week female; 1 standard drink = 14 g pure alcohol).

BAC Effects — Your Current Level

Legal BAC Limit Reference

BAC thresholds for the selected country. Your jurisdiction is highlighted.
Jurisdiction	Standard Limit	Zero Tolerance	Enhanced Penalty

Introduction

This BAC calculator helps you estimate your blood alcohol content based on what you drank, your body weight, your sex, and how much time has passed since your first drink. BAC stands for blood alcohol content, and it measures how much alcohol is in your blood as a percentage. A higher BAC means more alcohol in your system, which affects how you think, move, and react.

To use this tool, enter your personal details, add the drinks you had, and set the time since you started drinking. The calculator uses the Widmark formula to estimate your BAC and shows you how long it may take for your body to process the alcohol. It also displays the legal BAC driving limit for your state or country so you can see where you stand.

This tool is for educational purposes only. Many factors affect real BAC levels, including food intake, metabolism, medications, and overall health. No online calculator can replace a certified breathalyzer or blood test. Never rely on this estimate to decide whether it is safe to drive. If you have been drinking, always choose a sober driver, a rideshare, or another safe way home.

How to Use Our BAC Calculator

Enter a few details about yourself and what you drank. The calculator will estimate your blood alcohol content (BAC), show how long until you reach 0.00%, and display your risk level on a visual gauge and chart.

Biological Sex: Choose Male or Female. This affects how your body processes alcohol based on average body water differences.

Body Weight: Type in your weight and pick your unit: pounds, kilograms, or stones and pounds.

Country and State/Region: Select your country and jurisdiction. The calculator will load the correct legal BAC limits for your area.

Time Since First Drink: Choose "Elapsed Duration" and enter the hours and minutes since your first drink. Or choose "Clock Time" and enter the time you started drinking and whether it was today or yesterday.

Add Drinks: Use the Standard Table to pick a drink type like beer, wine, or liquor, then set the quantity, size, and ABV (alcohol by volume) and press the plus button. You can also use Quick Choices for common drinks or the Custom Creator to enter any drink by hand.

Standard Drink Units: If you know how many standard drinks you had but not the exact details, type that number here. One US standard drink equals about 14 grams of pure alcohol.

Drink Log: Review all the drinks you have added. You can remove any single drink or clear the entire list.

Calculate My BAC: Press this button to see your results. You will get your estimated BAC, a risk level badge, a color gauge, a timeline chart, countdown timers to 0.00% and your legal limit, a weekly guideline comparison, an effects breakdown, and a legal limit reference table for your selected region.

What Is Blood Alcohol Content (BAC)?

Blood alcohol content, or BAC, is a number that shows how much alcohol is in your blood. It is written as a percentage. For example, a BAC of 0.08% means there are 0.08 grams of alcohol for every 100 milliliters of your blood. The higher the number, the more alcohol is in your body and the more it affects you.

How Your Body Processes Alcohol

When you drink an alcoholic beverage, the alcohol goes into your stomach and small intestine. From there, it moves into your blood. Your liver breaks down most of the alcohol over time. On average, your body lowers your BAC by about 0.015% each hour. You cannot speed this up with coffee, food, or water. Only time brings your BAC back down to zero.

What Affects Your BAC Level

Several things change how high your BAC gets. Your body weight matters a lot. A heavier person will usually have a lower BAC than a lighter person after the same number of drinks. Biological sex plays a role too, because male and female bodies hold different amounts of water on average. Factors like body fat percentage can also influence how alcohol distributes through your system. How many drinks you had, how strong they were, and how much time has passed since your first drink all change the result as well.

What Counts as One Standard Drink

In the United States, one standard drink contains about 14 grams of pure alcohol. That equals roughly 12 ounces of regular beer at 5% alcohol, 5 ounces of wine at 12% alcohol, or 1.5 ounces of distilled spirits at 40% alcohol. Many cocktails and craft beers contain more alcohol than a single standard drink, so it is important to check the size and strength of what you are drinking.

Legal BAC Limits for Driving

Most U.S. states set the legal driving limit at 0.08% BAC. Utah uses a lower limit of 0.05%. Drivers under 21 face zero-tolerance laws in every state, meaning any detectable alcohol can lead to penalties. Other countries have their own limits. Canada and England use 0.08%, while Scotland and Australia set theirs at 0.05%. Going above these limits can result in arrest, fines, and loss of your driver's license.

Health Risks of High BAC

A BAC between 0.02% and 0.05% causes mild relaxation and slightly slower reactions. At 0.08% to 0.10%, your speech, balance, and judgment are clearly affected. Above 0.20%, you may feel confused or sick. A BAC at or above 0.30% puts you at serious risk of passing out, and levels above 0.40% can cause coma or death. If someone shows signs of alcohol poisoning, like slow breathing, pale skin, or being unable to wake up, call emergency services right away. Maintaining overall health through proper calorie intake and hydration can support your body's ability to process alcohol, but it will never make drinking excessive amounts safe.

Formulas used

Widmark BAC Estimation

BAC = \frac{A \times 5.14}{W \times r} - 0.015 \times H

Pure Alcohol (fl oz) from a Drink

A_{\text{drink}} = V_{\text{oz}} \times \frac{ABV}{100} \times Q

Pure Alcohol in Grams

A_g = A_{\text{oz}} \times 23.34

Standard Drinks Count

D_{\text{std}} = \frac{A_{\text{total\_oz}}}{0.6}

Time Until BAC Reaches Zero

t_{\text{zero}} = \frac{BAC}{0.015}

Time Until BAC Reaches Legal Threshold

t_{\text{legal}} = \frac{BAC - BAC_{\text{limit}}}{0.015}

Frequently asked questions

What is the Widmark formula?

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.

What does ABV mean?

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.

Why does biological sex change my BAC result?

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.

Why does body weight affect BAC?

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.

What is the 0.015 per hour rule?

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.

What is the difference between elapsed duration and clock time?

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, so pick whichever is easier for you.

How do I add a drink that is not listed?

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.

What is the Standard Drink Units field for?

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).

How is the time until 0.00% calculated?

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.

Does eating food lower my BAC?

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.

Can coffee or water sober me up faster?

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.

Why do the legal limits change when I pick a different country or state?

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.

What are zero tolerance and enhanced penalty limits?

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.

What are the volume units available for custom drinks?

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.

Is a BAC of 0.00% safe to drive?

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.

What should I do if someone has a very high BAC?

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.