Blood Alcohol Concentration (BAC) Calculator
Use our BAC calculator to estimate your blood alcohol level from beer, wine, or liquor. Everyone metabolizes alcohol differently.
Add drinks and personal information to calculate BAC
Our BAC calculator estimates blood alcohol concentration using the Widmark model. See current BAC, legal driving status, time to sober, and step-by-step calculation details.
Add beer, wine, or spirits by volume and ABV, enter your weight and time since drinking started, and read results in the panel on the right. This is an educational tool, not medical or legal advice.
How to Use This BAC Calculator
1. Select gender and enter body weight in lbs or kg.
2. Enter hours since your first drink (use 0 if you just started).
3. Choose drink type, amount in fl oz, ABV if custom, and how long ago you had each drink.
4. Click Add Drink for every beverage in your session.
5. Read current BAC, impairment level, legal status, time to sober, and calculation details in the results card.
How the Widmark BAC Formula Works
This calculator estimates BAC in percent using total ethanol in grams, body weight in grams, and a gender-based body-water constant (r). It then subtracts about 0.015% BAC per hour for metabolism.
Worked example
160 lb male, one 12 fl oz beer at 5% ABV, 1 hour after the drink (~14 g ethanol).
BAC ≈ (14 g ÷ (72,575 g × 0.68)) × 100 − (1 h × 0.015) ≈ 0.013%
Heavier people and spaced-out drinking usually lower BAC. Tracking weight over time? Pair this with our BMI calculator for general body metrics.
BAC Levels and Impairment
| BAC % | Typical effects | Driving (US adult) |
|---|---|---|
| 0.00–0.029 | Little or no obvious impairment | Generally legal |
| 0.030–0.059 | Mild euphoria, relaxed mood | Legal in most states |
| 0.060–0.079 | Impaired judgment and coordination | Use caution |
| 0.080+ | Legally intoxicated in most states | Do not drive |
| 0.200+ | Severe impairment, medical risk | Emergency care may be needed |
Alcohol also adds empty calories. If you track nutrition, our calorie calculator helps you log drink calories alongside meals.
For total daily burn including activity, see the TDEE calculator when you plan energy balance over a week.
Safety and Legal Disclaimer
Never drive, operate machinery, or make safety decisions from an online BAC estimate.
Under-21, commercial, and zero-tolerance rules are stricter than 0.08% in many places.
If you or someone else may have alcohol poisoning, call emergency services right away.
Frequently Asked Questions
Common questions about BAC calculators and sober-up myths
What is blood alcohol concentration (BAC)?
BAC is the percent of alcohol in your blood by volume. In the US, 0.08% often means 0.08 grams of alcohol per 100 mL of blood. That is the usual adult driving limit in most states.
How accurate is this BAC calculator?
It gives a rough estimate using the Widmark model and average metabolism. Real BAC depends on food, meds, liver health, and drink timing. Only a breath, blood, or lab test is accurate enough for legal or medical decisions.
What BAC is illegal to drive in the US?
For drivers 21 and older, 0.08% is the standard limit in most states. Utah uses 0.05%. Under-21 limits are often 0.01% to 0.02%. Commercial and enhanced penalties can apply at higher BAC levels.
How long until my BAC reaches zero?
This calculator assumes about 0.015% BAC cleared per hour. At 0.08% BAC, that is roughly 5 to 6 hours with no more drinks. Your real rate may be slower or faster.
Does coffee or water sober you up faster?
No. Coffee, cold showers, and water may help you feel awake, but they do not speed how fast your liver removes alcohol. Time is the only reliable way for BAC to drop.
How does body weight change BAC?
More body weight usually means more water volume to dilute alcohol, so BAC tends to be lower for the same drinks. Enter an honest weight in lbs or kg for a better estimate.
Why do men and women get different BAC results?
The Widmark model uses different body-water ratios (about 0.68 for men and 0.55 for women). Less water per pound of body weight often means a higher BAC for the same drinks.
How much alcohol is in one standard drink?
In the US, one standard drink is about 14 g of ethanol. That is roughly 12 fl oz beer at 5% ABV, 5 fl oz wine at 12% ABV, or 1.5 fl oz spirits at 40% ABV.
Can I use this result to decide if I can drive?
No. Use this for education only. If you have been drinking, use a designated driver, rideshare, or public transit. Never drive based on an online estimate.
How long after a drink does alcohol show up in blood?
Alcohol usually enters the bloodstream within 30 to 70 minutes after you drink. Peak BAC is often about 30 to 90 minutes after your last drink on an empty stomach.
What else affects BAC besides drinks and weight?
Food in your stomach, hydration, sleep, medications, and health conditions all matter. Drinking quickly raises BAC faster than spacing drinks over hours.
What does 0.08% BAC feel like?
At 0.08% many people show slower reactions, poorer judgment, and reduced coordination. Impairment can start well below 0.08%, so feeling fine is not a safe sign to drive.
Related Calculators
Calculators that pair well with BAC planning
Body Fat Calculator
Estimate body composition alongside weight used in BAC math.
Water Intake Calculator
Plan daily hydration, which affects how you feel after drinking.
Weight Converter
Convert body weight between lbs and kg before you enter it here.
Macro Calculator
Balance daily calories and macros when planning nights out.