BAC Calculator — Blood Alcohol Content
Estimate your blood alcohol content based on drinks consumed, body weight, gender, and time. For informational purposes only.
How to use this calculator
Select your gender and body weight, choose the type of drink, number of drinks, and how many hours since you started drinking. Your estimated BAC appears instantly using the Widmark formula — the same method used in law enforcement. Note: this is an estimate; actual BAC varies based on food intake, metabolism, medications, and other factors.
Understanding BAC
Blood alcohol content (BAC) is the percentage of alcohol in your bloodstream. The US legal limit for driving is 0.08%. Even below this, driving is impaired. BAC rises quickly — one drink can push some people over the limit — and falls at approximately 0.015% per hour as the liver metabolizes alcohol. Coffee, food, and water do not speed up this process.
Frequently asked questions
BAC effects by blood alcohol level
The effects of alcohol progress predictably as BAC rises. Note that tolerance can mask some subjective effects — a regular heavy drinker may feel less impaired at 0.10% than a rare drinker, but driving ability is impaired equally regardless of perceived intoxication.
| BAC level | Common effects |
|---|---|
| 0.02–0.03% | Slight relaxation, mild euphoria, subtle impairment in judgment |
| 0.04–0.06% | Feeling of warmth, relaxation, inhibitions lowered, minor impairment in reasoning |
| 0.07–0.09% | Impaired balance, speech, vision, reaction time; overconfidence; legally impaired in all US states (0.08% limit) |
| 0.10–0.12% | Significant impairment to coordination and judgment; slurred speech; clearly drunk |
| 0.13–0.15% | Gross impairment, dysphoria (discomfort), nausea possible, blurred vision |
| 0.16–0.20% | Nausea, vomiting, difficulty standing; loss of blackout risk begins |
| 0.21–0.25% | Stupor, unresponsiveness, severe impairment; medical emergency risk |
| 0.30%+ | Loss of consciousness, coma risk; potentially fatal |
| 0.40%+ | Risk of fatal respiratory depression; LD50 territory for many people |
Standard drink sizes in the US
One standard US drink contains 0.6 ounces (14 grams) of pure alcohol. Many cocktails, craft beers, and wine pours contain more than one standard drink — this is the most common source of BAC calculation error.
| Drink type | Serving size | Alcohol % | Standard drinks |
|---|---|---|---|
| Regular beer | 12 oz (355 mL) | 5% | 1.0 |
| Light beer | 12 oz (355 mL) | 4.2% | 0.8 |
| Craft IPA / strong beer | 12 oz (355 mL) | 7–9% | 1.4–1.8 |
| Table wine | 5 oz (148 mL) | 12% | 1.0 |
| Fortified wine (port) | 3 oz (89 mL) | 17% | 1.0 |
| Spirits (whiskey, vodka, gin) | 1.5 oz (44 mL) | 40% | 1.0 |
| Cocktail (e.g. Long Island iced tea) | Varies | Varies | 2–4 |
How the body processes alcohol
The liver metabolizes alcohol at a fixed rate of approximately 0.015% BAC per hour — roughly one standard drink per hour. This rate does not change with coffee, food, cold showers, or exercise. Only time reduces BAC.
- ·Absorption: alcohol enters the bloodstream through the stomach and small intestine within 30–90 minutes
- ·Food in the stomach slows absorption — drinking on an empty stomach produces higher, faster BAC peaks
- ·Women typically have lower body water percentage and less alcohol dehydrogenase (the enzyme that breaks down alcohol), resulting in higher BAC than men of the same weight drinking the same amount
- ·Genetic variation in alcohol dehydrogenase explains why some individuals — especially those of East Asian descent — flush more easily
- ·Carbonated mixers (champagne, sparkling water with spirits) speed up alcohol absorption vs. still mixers
- ·Regular heavy drinking does not speed up elimination — it increases tolerance (perceived effect) while actual BAC remains equally elevated
Alcohol and health — what the research shows
Current evidence no longer supports the previously popular claim that moderate drinking is beneficial. The safest level of alcohol consumption for overall health risk is zero, according to the Global Burden of Disease Study (2018) and subsequent large-scale research. However, the risk from moderate consumption is relatively small compared to heavy drinking.
- ·Cancer risk: alcohol is a Group 1 carcinogen (WHO); linked to 7 cancer types including breast, colon, liver, esophageal, and oral cancers
- ·Liver disease: heavy drinking leads to fatty liver, alcoholic hepatitis, cirrhosis, and liver cancer
- ·Cardiovascular: modest increases in risk of atrial fibrillation and stroke even at moderate levels
- ·Brain health: alcohol is neurotoxic; regular heavy drinking accelerates cognitive decline and brain shrinkage
- ·Weight: alcohol provides 7 cal/g (dense) and commonly increases appetite, leading to excess calorie intake
- ·Sleep: alcohol disrupts REM sleep and sleep architecture, reducing sleep quality even when it induces sleepiness