Health & Fitness
Blood Alcohol Calculator
Blood Alcohol — it estimates BAC with the Widmark formula — alcohol (g) ÷ (body weight × the sex constant) − 0.015 × hours since drinking. This page runs that same calculation on your numbers, in your browser: no signup, no uploads, nothing stored.
Blood Alcohol Calculator takes your body weight, sex, number of drinks and drink size and gives back an estimated BAC — a guide, never a sobriety test, applying the Widmark estimation. It's a quick, browser-based way to estimate blood alcohol concentration.
About this calculator
Get blood alcohol right and the rest of the task gets easier. It estimates BAC with the Widmark formula — alcohol (g) ÷ (body weight × the sex constant) − 0.015 × hours since drinking. It matters when you want a quick screening number before deciding whether a habit, plan or measurement deserves a closer look. For a 70 kg man, two 355 ml drinks at 5% ABV is about 2 × 355 × 0.05 × 0.789 ≈ 28 g of alcohol. The Widmark estimate is 28 ÷ (70,000 g × 0.68) × 100 ≈ 0.059% before metabolism is subtracted. The tool above does the same computation in your browser — free, private, nothing stored.
How to use
- Enter your body weight and select your sex.
- Enter the number of drinks, their size in ml, and ABV %.
- Enter hours since your first drink.
- Press Calculate to see an educational BAC estimate.
Why use Blood Alcohol Calculator
Fast
Calculations run in your browser. No round trip to a server.
Private
Your inputs never leave your device. Nothing is uploaded.
Free
No signup, no paywall, no ads-in-results, no watermarks.
Educational
Educational estimate only. Do not use this to decide whether to drive or for legal or clinical decisions.
Mobile-ready
Optimised for phones, tablets, and desktops alike.
Transparent
Clear about formulas used and their limits, with disclaimers where they matter.
Common uses
Blood Alcohol to understand the effect of time
Use it when pacing drinks at an event
Blood Alcohol as a general awareness guide
Use it for party and host planning
Use it for educational, harm-reduction use
Use it for understanding how alcohol adds up
Technical notes
Blood Alcohol Calculator estimates BAC with the Widmark formula — alcohol (g) ÷ (body weight × the sex constant) − 0.015 × hours since drinking. It is an estimate only, never a fitness-to-drive test.
These are general-population estimates and not a substitute for advice from a qualified clinician.
Results are rounded for display; the underlying calculation keeps full precision.
FAQ
How is BAC estimated here?
It uses the Widmark formula, dividing grams of alcohol by body water (from weight and a sex factor) and subtracting alcohol metabolised over time.
Why does sex change the BAC estimate?
The Widmark factor differs by sex because body-water proportion differs on average, so the same drinks can produce a higher estimated BAC for women than men.
Why is this not safe for driving decisions?
It is only an average model and ignores food, medication, and individual differences, so it can understate real impairment — never use it to judge fitness to drive.
Does the Blood Alcohol Calculator send my data to a server?
No. The Blood Alcohol Calculator runs entirely in your browser — your inputs never leave your device, and nothing is uploaded or stored.
Worked example
For a 70 kg man, two 355 ml drinks at 5% ABV is about 2 × 355 × 0.05 × 0.789 ≈ 28 g of alcohol. The Widmark estimate is 28 ÷ (70,000 g × 0.68) × 100 ≈ 0.059% before metabolism is subtracted. This is an educational estimate only — never use it to decide whether to drive.