BAC Calculator — a free online blood alcohol content estimation tool that calculates current BAC, time to zero, and safe driving time based on the Widmark formula, with support for US, UK, Australia, and New Zealand legal limits.
What is the BAC Calculator?
The BAC Calculator is a web-based tool that estimates your blood alcohol concentration using the Widmark formula with 2026 medical consensus data. You input your biological sex, weight (lbs or kg), region (US/AU/UK/NZ), then add drinks with volume and alcohol percentage. The tool outputs your estimated BAC, peak BAC, and time until you reach zero or the legal driving limit. It runs entirely in the browser with no registration required.
Key Features
- Time to Zero BAC Calculator — calculates when your BAC will return to zero based on your specific inputs; learn more about time to zero BAC calculations.
- When Can I Drive Calculator — estimates safe driving time using your region’s legal limit and includes safety buffers; see the detailed when can I drive calculator page.
- Standard Drinks Calculator — converts any drink (volume and ABV) into standard drink equivalents for US, UK, AU, and NZ standards; explore the standard drinks calculator guide.
- Multi-Market Support — automatically adjusts legal limits and standard drink definitions based on your selected region (US, UK, Australia, New Zealand).
- Real-Time BAC Estimation — instant updates as you add drinks or adjust time, with live preview using the Widmark formula.
- Hunger Level Input — accounts for absorption rate differences based on whether you’re full or hungry.
Who should use the BAC Calculator?
- Social drinkers who want to estimate when they will be sober enough to drive legally after an evening out.
- Party hosts who need a planning tool to help guests understand safe wait times before driving.
- Students or educators studying alcohol metabolism and wanting a practical demonstration of the Widmark formula.
- International travelers who move between US, UK, Australia, and New Zealand and need region-specific BAC estimates.
What can you do with the BAC Calculator?
- Estimate your current BAC: Enter your weight, sex, and drinks consumed to see a real-time BAC percentage and whether you’re over your region’s legal limit.
- Plan a night out: Pre-calculate how many standard drinks you can have over a given time to stay under 0.08% (US) or your local limit.
- Find when you’ll be safe to drive: Get a legally informed estimate of the time your BAC will drop below the legal threshold, using the when can I drive calculator.
How does the BAC Calculator work?
You start by selecting your region and entering your sex and weight. In step 2, you add each drink (type, volume, ABV) and optionally your hunger level. The tool instantly computes your BAC using the Widmark formula, adjusting for absorption rate and metabolism. The results screen shows your current BAC, estimated peak BAC, and the time when your BAC will reach zero or fall below the legal limit.
Pricing
The BAC Calculator is entirely free to use — no subscription, no hidden charges, and no account required.
FAQ
How accurate is the BAC estimation?
The tool uses the Widmark formula, the gold standard in forensic science, with 2026 medical consensus data. It accounts for weight, sex, absorption rate (hunger), and metabolism. However, individual factors like medications, health conditions, and recent food intake can cause real BAC to differ. The tool provides estimates only.
