BAC Calculator
Estimate your blood alcohol content (BAC) based on drinks consumed, body weight, gender, and time elapsed.
This calculator provides estimates only. Actual BAC varies based on many factors. Never drink and drive.
Widmark Formula
BAC Calculation
Variables
Understanding Blood Alcohol Content
Blood Alcohol Content (BAC) is the percentage of alcohol in your bloodstream. It's the standard measure used by law enforcement and medical professionals to assess intoxication levels.
BAC is affected by many factors including body weight, biological sex, food consumption, drinking speed, and individual metabolism. This calculator provides estimates based on the Widmark formula—the same method used in forensic alcohol calculations.
Legal Limits
0.08% BAC is the legal limit for driving in most US states. Some states use 0.05%.
Metabolism Rate
Your body eliminates alcohol at about 0.015% BAC per hour—roughly one drink.
Impairment Begins Early
Driving skills are impaired starting at 0.02% BAC—well below legal limits.
Individual Variation
Two people can drink the same amount and have different BAC levels.
BAC Levels and Effects
Alcohol affects your body progressively as BAC increases:
| BAC % | Typical Effects | Driving Ability | Legal Status |
|---|---|---|---|
| 0.01-0.03 | Mild relaxation, slight mood elevation | Minimal impairment | Legal |
| 0.04-0.06 | Lowered inhibitions, minor impairment of reasoning | Some impairment begins | Legal (most states) |
| 0.07-0.09 | Reduced coordination, impaired judgment, slowed reaction time | Significant impairment | Illegal in most states |
| 0.10-0.12 | Poor coordination, slurred speech, slowed thinking | Severely impaired | Illegal |
| 0.13-0.15 | Major loss of balance, blurred vision, anxiety | Very dangerous | Illegal |
| 0.16-0.19 | Dysphoria, nausea, disorientation | Extremely dangerous | Illegal |
| 0.20+ | Confusion, blackouts, risk of alcohol poisoning | Cannot drive | Medical emergency risk |
What Is a Standard Drink?
A 'standard drink' contains about 14 grams (0.6 oz) of pure alcohol. This equals:
Beer
12 oz of regular beer (5% ABV). Note: Craft beers, IPAs, and strong ales often contain 6-12% ABV—count these as 1.5-2+ drinks.
Wine
5 oz of wine (12% ABV). A typical restaurant pour is often 6-8 oz, and many wines are 13-15% ABV—so one 'glass' may equal 1.5+ standard drinks.
Spirits
1.5 oz of 80-proof (40% ABV) distilled spirits. Higher proof spirits contain more alcohol per pour.
Cocktails
Mixed drinks vary widely. A Long Island Iced Tea contains 3-4 standard drinks. A margarita may contain 1.5-2. A martini is about 2 standard drinks.
Factors That Affect BAC
Many factors beyond drink count influence your BAC:
Body Weight
Larger people have more blood volume, diluting alcohol. A 120 lb person will have higher BAC than a 200 lb person after the same drinks.
Biological Sex
Women typically have higher BAC than men of equal weight because of different body composition and water content. Women have a Widmark factor of ~0.55 vs ~0.68 for men.
Food in Stomach
Eating before or while drinking significantly slows alcohol absorption. Fatty foods are especially effective at slowing absorption.
Drinking Speed
Drinking quickly raises BAC faster than your body can metabolize alcohol. Spacing drinks over time results in lower peak BAC.
Medications
Many medications interact with alcohol, either increasing intoxication effects or slowing metabolism. Never mix alcohol with prescription drugs without consulting a doctor.
Fatigue and Stress
Being tired or stressed can intensify alcohol's effects even at the same BAC level. Your subjective impairment may exceed what BAC alone suggests.
How Alcohol Is Metabolized
Understanding how your body processes alcohol helps make informed decisions:
Alcohol is primarily metabolized by the liver at a relatively constant rate of about 0.015% BAC per hour (roughly one standard drink). This rate cannot be sped up by coffee, cold showers, or exercise—only time reduces BAC.
First-Pass Metabolism
Some alcohol is broken down in the stomach before reaching the bloodstream. This is more efficient in men and when food is present.
Peak BAC
BAC peaks about 30-45 minutes after your last drink on an empty stomach, or 1-2 hours with food. You may still be rising when you 'feel fine.'
Sleep Doesn't Speed It Up
Sleeping doesn't accelerate alcohol metabolism. If you go to bed drunk at 0.15% BAC, you may still be over 0.08% 5 hours later.
DUI/DWI Legal Information
Understanding legal limits is crucial for responsible drinking:
Standard Legal Limit
0.08% BAC is the per se legal limit in all 50 US states for drivers 21+. However, you can still be charged with impaired driving below this limit.
Zero Tolerance
Drivers under 21 face 'zero tolerance' laws in most states—any detectable BAC (often 0.01-0.02%) can result in penalties.
Commercial Drivers
Commercial vehicle operators (CDL holders) have a limit of 0.04% BAC while operating commercial vehicles.
Enhanced Penalties
BAC of 0.15% or higher often triggers 'aggravated DUI' charges with increased penalties including longer license suspension and mandatory jail time.
International Limits
Many countries use 0.05% BAC limits (Australia, most of Europe). Some countries (Japan, Sweden) use 0.02-0.03%. Others have zero tolerance.
Myths About Sobering Up
Common myths about reducing intoxication that don't actually work:
Coffee Doesn't Help
Caffeine may make you feel more alert, but it doesn't reduce BAC or improve coordination. You're just a 'wide-awake drunk.'
Cold Showers Don't Work
Cold water doesn't speed up alcohol metabolism. It may shock you awake temporarily but your BAC remains unchanged.
Exercise Doesn't Burn It Off
Physical activity doesn't significantly increase alcohol metabolism. It may even be dangerous due to impaired coordination and dehydration.
Eating After Doesn't Help Much
Once alcohol is in your bloodstream, food won't lower BAC. Eating only helps if done before or during drinking to slow absorption.
Frequently Asked Questions
How accurate is this BAC calculator?
This calculator uses the Widmark formula—the same method used in forensic alcohol calculations. However, individual variation is significant. Factors like genetics, liver health, medications, and exact alcohol content of drinks can cause actual BAC to differ from estimates by ±20% or more.
How long does it take to sober up?
Your body metabolizes alcohol at about 0.015% BAC per hour. If your BAC is 0.15%, it takes about 10 hours to reach 0.00%. If you stop drinking at 2 AM with a 0.12% BAC, you may still be legally impaired at 8 AM.
Is it safe to drive if I'm under 0.08%?
No. Impairment begins at BAC levels as low as 0.02%. Studies show increased crash risk starting at 0.05% BAC. The legal limit is not a 'safe' limit—it's simply where criminal penalties begin. If you've been drinking, don't drive.
Why do I feel drunker than my BAC suggests?
Many factors affect subjective intoxication: fatigue, medications, tolerance level, mood, and drinking speed. Also, you feel more impaired when BAC is rising than when it's falling at the same level (Mellanby effect).
What's the difference between BAC and BrAC?
BAC (Blood Alcohol Content) is measured from blood samples. BrAC (Breath Alcohol Content) is measured by breathalyzers. They're highly correlated, with a breath-to-blood ratio of approximately 2100:1 used for conversion.
Can I beat a breathalyzer test?
No. Common myths—hyperventilating, holding breath, using breath mints—don't work. Modern breathalyzers are designed to account for these attempts. Some tactics can actually increase readings.
How many drinks can I have and still drive?
There's no universally safe number. A 120 lb woman may exceed 0.08% after 2 drinks, while a 200 lb man might be under 0.08% after 3. However, impairment begins with the first drink. The only safe answer: if you plan to drive, don't drink at all.
Does tolerance affect BAC?
No. Tolerance affects how impaired you feel, not your actual BAC. A heavy drinker may feel functional at 0.15% BAC where a light drinker would be severely impaired—but both have the same legal BAC and similar physiological impairment in reaction time and coordination.
Pro Tips
- Bookmark this calculator for quick access in the future
- Use the share button to send your results to others
- Try different scenarios to compare outcomes
- Check out our related calculators for more insights
Found this calculator helpful? Share it with others: