BAC Calculator
Estimate your Blood Alcohol Content (BAC) instantly using the Widmark formula — the standard model used in forensic toxicology. Enter your drinks using 12 presets or custom values, your weight, biological sex, and hours since your first drink to get your estimated current BAC, peak BAC, time to reach the legal limit, and time to fully sober. No signup required — all calculations run locally in your browser.
Enter your drinks, weight, gender, and time elapsed since your first drink to estimate your current Blood Alcohol Content using the Widmark formula. All calculations run locally in your browser — your data never leaves your device.
0 = right now
BAC = (Alcohol grams / (Weight kg × r × 10)) − (0.015 × Hours)
- r = Widmark factor: 0.68 (male), 0.55 (female)
- Alcohol grams = Volume (ml) × ABV% × 0.789 (ethanol density)
- Metabolism rate: ~0.015% BAC per hour (average)
Why Use Our BAC Calculator?
Instant BAC Calculation
Calculate your estimated Blood Alcohol Content instantly in your browser with zero wait time. Our BAC calculator uses the Widmark formula to compute peak BAC, current BAC, time to sober, and time to legal limit in milliseconds.
Secure BAC Calculator Online
All BAC calculations happen locally in your browser — your weight, drink data, and personal information never leave your device. Use our BAC calculator online with complete privacy and zero data collection.
BAC Calculator — No Installation
Use our BAC calculator directly in any browser with no downloads, plugins, or app installs required. Calculate your estimated BAC from any device, anywhere — desktop, tablet, or mobile — instantly.
12 Drink Presets + Custom Drinks
Our BAC calculator includes 12 common drink presets — beer, wine, spirits, cocktails, and cider — with pre-filled volume and ABV values. Add multiple drinks, adjust quantities, and use the custom option for any drink not in the list.
Common Use Cases for BAC Calculator
Responsible Driving Decisions
Use our BAC calculator before deciding whether to drive after drinking. Knowing your estimated BAC and the time remaining until you reach the legal limit helps you make an informed, responsible decision about getting behind the wheel.
Pre-Event Drink Planning
Plan your drinks at a party, wedding, or event by estimating your BAC in advance. Our BAC calculator lets you model different drink scenarios so you can enjoy the event while staying within safe limits.
Understanding Alcohol Metabolism
Use our BAC calculator to understand how your body processes alcohol over time. Seeing the time-to-sober estimate helps you plan when it is safe to drive, operate machinery, or take medication after drinking.
Harm Reduction & Safety Education
Health educators and harm reduction organisations use BAC calculators to help people understand the relationship between drinks, body weight, and impairment. Our BAC calculator makes this information accessible and easy to understand.
Workplace & Occupational Safety
Workers in safety-critical industries use the BAC calculator to estimate when they will be fully sober after an evening of drinking before an early morning shift. Knowing your time-to-sober helps you plan responsibly.
Medical & Pharmacology Reference
Healthcare students and professionals use BAC calculators to understand alcohol pharmacokinetics. The Widmark formula is the standard model used in forensic toxicology and clinical pharmacology for estimating blood alcohol levels.
Understanding BAC Calculation
What is BAC and How is it Calculated?
Blood Alcohol Content (BAC) is the concentration of alcohol in your bloodstream, expressed as a percentage. A BAC of 0.08% means 0.08 grams of alcohol per 100 millilitres of blood. Our BAC calculator uses the Widmark formula — the standard model used in forensic toxicology and clinical pharmacology: BAC = (Alcohol grams ÷ (Weight kg × r × 10)) − (0.015 × Hours elapsed). The Widmark factor (r) accounts for the difference in body water distribution between males (0.68) and females (0.55), which is why women typically reach higher BAC levels than men of the same weight drinking the same amount.
How Our BAC Calculator Works
- 1. Enter Your Drinks: Add each drink using the presets (beer, wine, spirits, cocktails) or enter custom volume and ABV values. The calculator converts each drink to grams of pure ethanol using: Alcohol grams = Volume (ml) × ABV% × 0.789. All processing happens locally in your browser — your data never leaves your device.
- 2. Enter Your Details: Input your weight, biological sex, and the number of hours since your first drink. Sex affects the Widmark factor (r), and weight directly determines how alcohol is distributed through your body.
- 3. Get Your BAC Estimate: Click Calculate BAC to see your estimated current BAC, peak BAC, time to reach the legal limit, and time to fully sober — with a full breakdown and BAC effects reference table.
Key Factors That Affect BAC
- Body Weight: Heavier individuals have more body water to dilute alcohol, resulting in lower BAC for the same amount of alcohol. A 90 kg person will have a significantly lower BAC than a 60 kg person drinking the same drinks.
- Biological Sex: Women typically have a lower Widmark factor (0.55 vs 0.68 for men) due to differences in body water percentage and alcohol dehydrogenase enzyme activity. This means women generally reach higher BAC levels than men of the same weight.
- Food Intake: Eating before or during drinking significantly slows alcohol absorption, reducing peak BAC. Our BAC calculator assumes drinking on an empty stomach — actual BAC may be lower if you have eaten.
- Metabolism Rate: The average alcohol metabolism rate is approximately 0.015% BAC per hour, but this varies between individuals based on liver enzyme activity, genetics, and regular alcohol consumption. Our BAC calculator uses the standard average rate.
Legal BAC Limits by Country
Legal BAC limits for driving vary by country. The UK (England, Wales, Northern Ireland) limit is 0.08%. Scotland and most EU countries apply a stricter 0.05% limit. The USA federal limit is 0.08% for drivers over 21. Many countries including Japan, Brazil, and Hungary apply a near-zero limit of 0.02–0.03%. Our BAC calculator shows the time to reach both the 0.08% and 0.05% thresholds so you can apply the relevant limit for your jurisdiction. Never drive if you have been drinking — even below the legal limit, alcohol impairs reaction time and judgment.
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Frequently Asked Questions About BAC Calculator
What is a BAC calculator?
A BAC calculator estimates your Blood Alcohol Content — the concentration of alcohol in your bloodstream — from the drinks you have consumed, your weight, biological sex, and time elapsed. Our BAC calculator uses the Widmark formula, the standard model used in forensic toxicology. All calculations run locally in your browser with no data sent to any server.
How accurate is the BAC calculator?
Our BAC calculator provides a scientifically grounded estimate using the validated Widmark formula. However, actual BAC varies with food intake (eating reduces peak BAC), hydration, medications, individual metabolism, and liver enzyme activity. The estimate is most accurate when drinking on an empty stomach. Always treat the result as an estimate, not a precise measurement.
What is the legal BAC limit for driving?
Legal BAC limits vary by country. England, Wales, Northern Ireland, and the USA apply a 0.08% limit. Scotland and most EU countries apply a stricter 0.05% limit. Japan, Brazil, and Hungary apply near-zero limits of 0.02–0.03%. Our BAC calculator shows the time to reach both 0.08% and 0.05% thresholds. Never drive after drinking — even below the legal limit, alcohol impairs driving ability.
Why does biological sex affect BAC?
Women typically have a lower Widmark factor (0.55) than men (0.68) due to differences in body water percentage and lower levels of alcohol dehydrogenase enzyme in the stomach. This means women generally reach higher BAC levels than men of the same weight drinking the same amount of alcohol.
How long does it take to sober up?
The average alcohol metabolism rate is approximately 0.015% BAC per hour. To estimate your time to sober, divide your current BAC by 0.015. For example, a BAC of 0.12% takes approximately 8 hours to reach 0.00%. Coffee, food, water, and exercise do not speed up alcohol metabolism — only time does.
Does eating affect BAC?
Yes — significantly. Eating before or during drinking slows alcohol absorption into the bloodstream, reducing peak BAC by 20–50%. Our BAC calculator assumes drinking on an empty stomach, so your actual BAC may be lower if you have eaten. Food does not speed up alcohol metabolism — it only slows absorption.
Is this BAC calculator free to use?
Yes! Our BAC calculator is 100% free with no signup, no ads, and no usage limits. Calculate your estimated BAC as many times as you need — completely free, forever.
Is my data safe when using this BAC calculator?
Absolutely. All BAC calculations happen locally in your browser using JavaScript. Your weight, drink data, and personal information are never sent to any server, ensuring complete privacy every time you use our BAC calculator online.
Can I use this BAC calculator for any country?
Yes — our BAC calculator works globally. It shows the time to reach both 0.08% (UK/US limit) and 0.05% (Scotland/EU limit) so you can apply the relevant legal limit for your jurisdiction. Always check the specific legal limit in your country or state before driving.