BAC Calculator
Estimate your blood alcohol concentration from your body weight, what you drank and how long ago you started. See how it may change over the next few hours.
Compare with a driving limit
Limits differ by country, state and type of licence. Check the rules where you live.
When will it drop?
Estimated using your selected clearing speed. Treat these as rough guides, not guarantees.
Projected BAC over time
If you stop drinking now, your BAC is estimated to fall in a straight line.
Your drinks in numbers
What this level may feel like
Effects by BAC level
Your estimated range is highlighted.
| BAC (%) | Typical behavior | Typical impairment |
|---|
Tips and safety suggestions
Good to know
What is blood alcohol concentration?
BAC is the share of alcohol in your blood. A BAC of 0.08% means 0.08 grams of alcohol in every 100 milliliters of blood. Some countries show the same value per thousand, so 0.08% equals 0.8 per mille (0.8 g/L).
How does this calculator work?
It uses the Widmark formula. It works out the grams of pure alcohol in your drinks, divides that by your body weight multiplied by a body water factor (0.68 for men, 0.55 for women), then subtracts the alcohol your body has cleared since you started drinking.
How accurate is the result?
It is an estimate only. Food in your stomach, how fast you drank, body fat, age, medication, health conditions, genetics and drinking habits all change your real BAC, and none of them are in the formula. A breathalyser or blood test is the only reliable measure.
What is a standard drink?
In the US, a standard drink holds about 14 grams of pure alcohol. That is roughly 12 oz (350 ml) of 5% beer, 5 oz (150 ml) of 12% wine or 1.5 oz (45 ml) of 40% spirits. In the UK, one unit is 10 ml (8 g) of pure alcohol.
Does coffee, water or a cold shower sober you up?
No. Only time lowers your BAC, because your liver clears alcohol at a fairly steady pace. Coffee can make you feel more alert without making you any safer to drive.
Can I drive if I am under the limit?
Alcohol can affect reaction time, judgement and vision at levels below legal limits. The safest choice is to avoid driving after drinking at all. Plan a taxi, rideshare, public transport or a designated driver in advance.
BAC Calculator: Estimate Your Blood Alcohol Level in Seconds
Have you ever wondered how much alcohol is really in your blood after a few drinks? Our free BAC calculator gives you a clear estimate in seconds. Enter your weight, the drinks you had and how long ago you started, and the tool shows your blood alcohol concentration, how impaired you may be and roughly when you could be sober again.
It is built to be simple, private and easy to understand, whether you are planning a night out or just curious about how alcohol works.
What Is Blood Alcohol Concentration (BAC)?
Blood alcohol concentration, or BAC, is the percentage of alcohol in your bloodstream. A BAC of 0.08% means there are 0.08 grams of alcohol in every 100 milliliters of blood. Many countries also express it per thousand, so 0.08% equals 0.8 per mille (0.8 g/L).
BAC is the most common way to measure how drunk someone is, and it is the number most laws use to set driving limits.
How to Use BAC Calculator
Using the tool takes less than a minute:
- Choose your sex and enter your body weight in kilograms, pounds or grams.
- Add the time since your first drink in hours and minutes.
- Add your drinks. Pick beer, wine, liquor or any other drink, then choose the amount, size and ABV (alcohol by volume).
- Press Calculate BAC to see your results instantly.
You can add as many drink lines as you need, so mixed nights are easy to enter.
Key Features of This BAC Calculator
This is more than a single number. The tool is designed to give you the full picture:
- Live BAC gauge: A colored dial shows where you sit, from sober to dangerous.
- Multiple drinks: Combine beer, wine, spirits and custom drinks in one calculation.
- Driving limit comparison: Compare your result with limits from 0.08% down to zero tolerance.
- Sober-up timer: See about how long until you are under the limit and back to 0.000%.
- Projection chart: A simple graph shows how your BAC may fall over the next hours.
- Standard drinks and calories: Find out your total pure alcohol, US standard drinks, UK units and calories from alcohol.
- Clearing speed setting: Choose a slow, average or fast rate to match your situation.
- Safety tips: Advice changes with your result, including warnings at dangerous levels.
- Copy and print: Save your results in one click.
How Is BAC Calculator Calculate? The Widmark Formula
The BAC Calculator uses the Widmark formula, the standard method for estimating BAC. First, it works out the grams of pure alcohol in your drinks from their volume and ABV. It then divides that by your body weight multiplied by a body water factor, which is 0.68 for men and 0.55 for women. Finally, it subtracts the alcohol your body has cleared, at an average of about 0.015% per hour. This gives a reliable estimate for most adults, but it is still an estimate.
What Affects Your BAC?
Two people can drink the same amount and reach very different levels. Factors that change your real BAC include:
- Body weight and composition: Smaller people and those with more body fat usually reach higher BAC.
- Sex: Women often reach a higher BAC from the same number of drinks.
- Food: Eating slows absorption and lowers your peak.
- Drinking speed: Fast drinking raises BAC more quickly.
- Medication and health: Some drugs and medical conditions change how alcohol is processed.
- Tolerance and genetics: These affect how alcohol feels and how fast you clear it.
BAC Levels and Their Effects
| BAC (%) | What you may notice |
| 0.01 – 0.03 | Barely noticeable, subtle changes only |
| 0.03 – 0.06 | Relaxed, talkative, lower inhibitions |
| 0.06 – 0.10 | Poorer judgement, vision and reasoning |
| 0.10 – 0.20 | Slurred speech, poor balance, slow reactions |
| 0.20 – 0.30 | Confusion, vomiting, memory blackouts |
| 0.30 and above | Danger of unconsciousness and life-threatening effects |
Legal BAC Limits
Driving limits vary around the world. Many places in the United States use 0.08%, while a large number of countries use 0.05% or lower, and some apply zero tolerance for young or professional drivers. Our calculator lets you compare your result against several common limits. Always check the law where you live, and remember that impairment begins well below the legal limit.
Tips for Drinking Responsibly
- Plan your ride first. Arrange a taxi, rideshare or designated driver before you start drinking.
- Alternate with water. It slows your pace and helps you stay hydrated.
- Eat a proper meal. Food slows alcohol absorption.
- Know what is in your glass. Large pours and strong drinks often equal more than one standard drink.
- Do not rely on myths. Coffee, cold showers and fresh air do not lower your BAC. Only time does.
- Look after your friends. Stay with anyone who has had too much, and call emergency services if they cannot be woken.
Try the BAC Calculator Now
Knowing your estimated BAC helps you make safer choices. Use the calculator above, check your result against your local limit, and always choose a safe ride home. This tool is for information only and is never a substitute for a breathalyser or good judgement.
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Also visit our website for payoff calculators at: All Payoff Calculators
Frequently Asked Questions: BAC calculator
1. How accurate is a BAC calculator?
A BAC calculator gives a good estimate, but not an exact reading. It cannot account for food, medication, health conditions or genetics. Only a breathalyser or blood test can measure your true BAC.
2. How long does it take to sober up?
On average, the body clears about 0.015% BAC per hour, so a BAC of 0.08% takes around five to six hours to reach zero. The speed varies from person to person, and nothing can make it faster.
3. How many drinks does it take to reach 0.08% BAC?
It depends on your weight, sex, the strength of the drinks and how fast you drink. As a rough guide, a 70 kg man may reach 0.08% after about three to four standard drinks in an hour or two, while a smaller person may get there sooner. Enter your details in the calculator for a personal estimate.
4. Can I drive if my BAC is below the legal limit?
It is not safe to assume so. Alcohol can slow reactions and weaken judgement below legal limits, and some drivers face lower limits or zero tolerance. The safest choice is not to drive after drinking.
5. What is a standard drink?
In the US, a standard drink contains about 14 grams of pure alcohol. That is roughly 350 ml of 5% beer, 150 ml of 12% wine or 45 ml of 40% spirits. In the UK, one unit equals 10 ml of pure alcohol.
