BAC Calculator — Free Blood Alcohol Estimator
Estimate blood alcohol content from weight, drinks, and time using the Widmark formula — educational estimates only.
Tool Interface
| BAC | Typical effects |
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How to use
- Choose your weight units (lb or kg) and gender.
- Enter your body weight, the number of standard drinks consumed, and hours since your first drink.
- Press Calculate BAC to see your estimated blood alcohol content, the matching effects band, and estimated hours until sober — all computed in your browser.
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About This Tool
Introduction
How alcohol affects you depends on your weight, gender, how much you drank, and how much time has passed. Trencada's free BAC Calculator applies the widely used Widmark formula to those four inputs and gives an estimated blood alcohol content, the matching impairment-effects band, and an estimate of hours until sober. The result is clearly labeled as an estimate — individual results vary widely, and the tool prominently reminds you never to drink and drive. Everything runs entirely in your browser with no signup and no downloads.
How to Use
- Choose your weight units (lb or kg) and gender (used for the Widmark body-water constant).
- Enter your body weight, the number of standard drinks (12 oz beer = 5 oz wine = 1.5 oz spirits), and hours since your first drink.
- Press Calculate BAC to see your estimated BAC, the effects band it falls in, and estimated hours until sober — all computed in your browser.
Key Features
- Widmark formula with gender-specific constants (0.73 male / 0.66 female)
- lb/kg weight toggle with automatic conversion
- Color-coded impairment bands with a typical-effects reference table
- Estimated hours until sober
- Prominent safety disclaimer on every result — never drink and drive
- Fully responsive — works on phones, tablets, and desktops
Why Choose Trencada
Every Trencada tool is free forever with no hidden costs, no accounts, and no installation. The BAC Calculator runs 100% in your browser, so nothing you enter is uploaded, stored, or tracked.
Frequently Asked Questions (FAQ)
- How is BAC estimated? With the Widmark formula: BAC% = (drinks × 0.6 oz × 5.14 ÷ (weight in lb × r)) − 0.015 × hours, where r is 0.73 for males and 0.66 for females. Results are floored at zero.
- Can I drive if the calculator says my BAC is low? No. Never use this or any calculator to decide whether to drive. Estimates vary widely by individual, food, medications, and tolerance — if in doubt, do not drive.
- What is a standard drink? In the US: 12 oz of beer (5% ABV), 5 oz of wine (12% ABV), or 1.5 oz of spirits (40% ABV) — each contains about 0.6 oz of pure alcohol.
- Is this medical or legal advice? No. This is an educational estimate only. It is not medical or legal advice, and it cannot tell you whether you are safe or legal to drive.
- Is my data private? Yes. The tool runs entirely in your browser — nothing you enter leaves your device.