BAC Calculator
Drinks consumed:
What Is a BAC Calculator?
A BAC (Blood Alcohol Content) calculator estimates the concentration of alcohol in your bloodstream based on the number of drinks consumed, your body weight, biological sex, and how much time has passed. BAC is expressed as a percentage — 0.08% means 0.08 grams of alcohol per 100 milliliters of blood.
This calculator uses the Widmark formula — the most widely used method in forensic toxicology — which accounts for the difference in body water distribution between males (r=0.68) and females (r=0.55), because higher body fat percentage means alcohol is more concentrated in less total body water.
Important: This is an educational estimate only. Actual BAC varies based on food consumed, medications, individual metabolism, liver health, and other factors. Never make driving decisions based on any calculator — use a certified breathalyzer or simply don't drive after drinking.
How to Use This BAC Calculator
- Select your biological sex (affects body water distribution).
- Enter your weight in pounds.
- Enter the number of hours since your first drink.
- Select the drink type and quantity for each drink consumed. Add rows for multiple drink types.
- Click Estimate BAC to see your estimated BAC percentage and hours until sober.
BAC Effects Reference
| BAC Level | Effects | Legal Status |
|---|---|---|
| 0.01–0.03% | Mild relaxation, slight euphoria | Legal everywhere |
| 0.04–0.06% | Lowered inhibitions, reaction time beginning to slow | Legal (caution) |
| 0.07–0.10% | Impaired judgment, balance, and coordination | Illegal to drive in all US states at 0.08%+ |
| 0.11–0.15% | Slurred speech, significant motor impairment | Illegal, DUI |
| 0.16–0.30% | Severe impairment, possible blackout | Extreme DUI / DWI |
| 0.31%+ | Life-threatening, risk of coma | Medical emergency |
Standard Drink Equivalents
A "standard drink" in the US contains 14 grams of pure alcohol. The following all equal one standard drink:
- Beer: 12 fl oz at 5% ABV
- Wine: 5 fl oz at 12% ABV
- Spirits: 1.5 fl oz (shot) at 40% ABV
- Hard seltzer: 12 fl oz at 5% ABV
- Craft beer: Many craft beers are 7–10% ABV — a 12 oz craft IPA can equal 1.5–2 standard drinks
How BAC Is Metabolized
- Elimination rate: The liver processes alcohol at approximately 0.015% BAC per hour for most people. You cannot speed this up with coffee, food, or exercise after drinking.
- Food effect: Eating before and during drinking slows alcohol absorption by 30–50% — food does not affect elimination, but it significantly lowers peak BAC.
- Carbonation accelerates absorption: Sparkling wines and champagne are absorbed faster than still wines of the same ABV.
- Tolerance changes behavior, not BAC: Habitual drinkers who "feel fine" at 0.08% still have the same impaired reflexes and judgment — they just don't feel it.
Frequently Asked Questions About BAC
What BAC is legally drunk?
In all 50 US states, the legal limit for driving is 0.08% for adults 21+. Commercial drivers face a 0.04% limit. Drivers under 21 face zero-tolerance laws (typically 0.00–0.02%).
How many drinks does it take to reach 0.08%?
It varies by weight and sex. For a 160 lb male: approximately 4 standard drinks in 2 hours on an empty stomach. For a 130 lb female: about 2–3 drinks. Always use the calculator with your actual numbers.
How long does it take for BAC to go back to 0?
At the standard elimination rate of 0.015%/hour: a 0.08% BAC takes about 5.3 hours to reach zero. A 0.15% BAC takes about 10 hours. Sleep does not speed up metabolism.
Does drinking water lower BAC?
Water does not lower BAC — only time does. Water can help you feel better and prevents dehydration, but it has no effect on how fast your liver metabolizes alcohol.
Why do women have higher BAC than men after the same drinks?
Women generally have a lower body water percentage (55% vs 68% for men). Since alcohol distributes through body water, the same amount of alcohol becomes more concentrated in women's bloodstream. Weight differences also play a role.
Can I pass a breathalyzer test with a certain BAC?
A breathalyzer measures alcohol in your breath, which correlates with blood alcohol. The only way to pass a breathalyzer is to not drink, or to wait until your BAC has fully metabolized to 0.00%. No tricks or shortcuts work reliably.
What is the Widmark formula for BAC?
BAC = (alcohol in grams) ÷ (body weight in grams × r), where r is 0.68 for males and 0.55 for females. Then subtract 0.015 × hours elapsed to account for metabolism. This is the basis of most BAC calculators and legal forensic estimates.
Is 0.06% BAC safe to drive?
No. While 0.06% is below the legal limit, research shows that driving ability is measurably impaired starting at 0.04%. At 0.06%, reaction time, lane-keeping, and hazard response are all degraded. "Legal" does not mean "safe."