Blood Alcohol Content (BAC) Calculator
The Widmark formula behind every BAC chart — and the honest reasons it can never tell you it is safe to drive.
Estimate your BAC
One standard drink = 12 oz beer (5%) · 5 oz wine (12%) · 1.5 oz spirits (40%)
The Widmark formula
Every BAC chart descends from Erik Widmark's 1932 equation: alcohol consumed (grams) divided by body weight times a distribution constant (≈0.68 for men, 0.55 for women — alcohol distributes into body water, and body composition differs), minus elimination of roughly 0.015% per hour. A standard US drink contains about 14 grams of alcohol regardless of whether it is beer, wine, or whiskey.
Why your real BAC can be higher than this estimate
The formula assumes textbook conditions. Reality intervenes: drinks are over-poured (a generous wine pour or a craft IPA can be 1.5–2 "standard" drinks), empty stomachs speed absorption, medications interact, fatigue amplifies impairment, and individual metabolism varies. Police breathalyzers do not care about your calculator. Treat every estimate as a floor, not a ceiling.
The numbers that matter — and the one rule
Impairment begins around 0.02% — divided attention and tracking degrade long before anyone feels "drunk." At 0.05%, crash risk roughly doubles; at 0.08% (the legal limit in most US states; 0.05% in Utah) it is several times baseline. Commercial drivers are held to 0.04%, under-21 drivers to near zero. Elimination cannot be rushed: coffee, cold showers, and food make you an alert person with the same BAC. The only honest use of this calculator is appreciating how long alcohol persists — three drinks can take five-plus hours to fully clear. If you have been drinking at all, the driving decision is already made: ride share, taxi, or a sober friend. In Las Vegas, the ride costs less than the valet at most casinos — and infinitely less than a DUI.
Frequently asked questions
How long until I am at zero?
Elimination averages ~0.015% per hour and nothing accelerates it. The calculator shows the estimate — note that one evening of heavy drinking can leave measurable BAC the next morning.
Is 0.08 the limit everywhere?
It is the standard in most US states; Utah uses 0.05, commercial drivers face 0.04, and under-21 drivers face zero-tolerance limits. You can also be charged below 0.08 if demonstrably impaired.
Why do women reach higher BAC on the same drinks?
On average lower body water percentage (the Widmark r of 0.55 vs 0.68), so the same alcohol concentrates more. Body size compounds the effect.
Does eating before drinking lower BAC?
Food slows absorption, flattening the peak — but the same alcohol still enters your blood and takes just as long to eliminate. It buys gentleness, not sobriety.
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How BAC is calculated — the Widmark formula
Blood alcohol concentration is most commonly estimated using the Widmark formula, developed by Swedish researcher Erik Widmark in 1932 and still the standard for forensic blood alcohol estimation: BAC = (Alcohol consumed in grams) ÷ (Body weight in grams × Widmark factor) × 100. The Widmark factor (r) accounts for body water distribution: approximately 0.68 for men, 0.55 for women. Alcohol in grams is calculated from: volume × ABV% × 0.789 (the specific gravity of ethanol). Elapsed time reduces BAC by roughly 0.015%/hour (the average liver metabolism rate).
A standard US drink contains approximately 14 grams of pure alcohol: 12 oz of 5% beer, 5 oz of 12% wine, or 1.5 oz of 80-proof spirits. Drinks vary significantly — a 9% craft IPA in a 16 oz pour is over 2 standard drinks; a 15% wine pour of 6 oz is 1.8 standard drinks. Actual BAC depends on your actual drink contents, not just the number of drinks.
BAC thresholds and their effects
- 0.02–0.03%: Mild relaxation, slight euphoria, minimal impairment for most people
- 0.05–0.07%: Reduced inhibitions, impaired judgment and fine motor control, overconfidence about ability to drive — the most dangerous zone for driving because people feel capable but are measurably impaired
- 0.08%: Legal DUI limit in all 50 US states. Reaction time, coordination, and judgment are significantly impaired
- 0.10–0.15%: Significant impairment across all driving-relevant functions; slurred speech, poor coordination
- 0.15–0.25%: Severe impairment, possible vomiting, disorientation
- 0.25%+: Potential loss of consciousness; medical emergency territory
Las Vegas DUI laws — what you need to know
Nevada DUI law (NRS 484C.110) establishes: BAC of 0.08%+ is per se DUI for drivers 21+. BAC of 0.04%+ is DUI for commercial vehicle operators. Any detectable BAC is DUI for drivers under 21. Penalties for first-offense Nevada DUI: 2–180 days in jail (or community service), $400–$1,000 fine plus assessments, 185-day license revocation, mandatory DUI school, possible ignition interlock device. Second offense within 7 years: mandatory 10 days jail, increased fines. Nevada has no "wet reckless" plea for standard DUI charges.
Las Vegas is one of the most active DUI enforcement environments in the country — the concentration of bars, clubs, and entertainment venues combined with a transient visitor population means DUI checkpoints and saturation patrols are common, particularly on weekends and holidays.
Why this calculator is not a substitute for common sense
BAC estimation from body weight and drinks is inherently imprecise. Individual elimination rates vary from 0.010%/hr to 0.025%/hr — the 0.015%/hr average used by most calculators is accurate for the population but not for any specific individual. Medications, food intake, hydration, tolerance, and fatigue all affect how alcohol feels and how impaired you actually are, independent of BAC. The safest decision: if you have had any drinks, plan transportation in advance. Las Vegas has abundant Uber, Lyft, and taxi options — use them.
Frequently asked questions
How many drinks does it take to reach 0.08% BAC?
It depends on body weight and time. For a 160-lb man: roughly 3–4 standard drinks in one hour can reach 0.08%. For a 120-lb woman: 2–3 standard drinks can reach 0.08%. These are rough estimates — individual metabolism rates vary by 2.5× across the population. The only safe number for driving is zero.
Does eating food lower BAC?
Food slows alcohol absorption from the stomach into the bloodstream — it does not reduce total alcohol absorbed. Eating before or during drinking means BAC rises more slowly and peaks at a lower level, but the same total alcohol is eventually absorbed. Food does not "sober you up" — only time and liver metabolism reduce BAC. Water rehydrates; it does not accelerate alcohol elimination.
How long does it take to sober up?
On average, the liver metabolizes alcohol at about 0.015% BAC per hour. At a BAC of 0.12%, that is approximately 8 hours to return to 0.00%. At 0.08%, about 5–6 hours. Coffee, water, food, cold showers, and sleep do not speed this up — only time does. Many DUI arrests occur in the morning by people who thought they had slept it off.
What is Nevada's DUI penalty for a first offense?
First-offense Nevada DUI: 2–180 days in jail (often community service for first offense), $400–$1,000 fine plus court assessments (total cost often $3,000–$5,000+), 185-day license revocation, mandatory DUI school, and possible ignition interlock device requirement. A Nevada DUI conviction also appears on your driving record and may affect employment, insurance rates, and professional licenses.
Can you refuse a breathalyzer in Nevada?
Nevada has an implied consent law (NRS 484C.150): by driving on Nevada roads, you consent to chemical testing if lawfully arrested for DUI. Refusing a breathalyzer or blood test results in mandatory license revocation of 1 year for a first offense (longer for subsequent), and the refusal can be used as evidence against you in court. It does not prevent DUI prosecution — police can obtain a warrant for a blood draw.
Disclaimer: This calculator provides a rough estimate of BAC for general educational purposes only. It is not accurate enough to determine whether you are legally safe to drive. Individual metabolism rates, medications, health conditions, and other factors significantly affect actual BAC. Never drive after drinking, regardless of calculated BAC. BAC estimates should never substitute for professional legal advice, medical evaluation, or the decision to arrange alternative transportation.