⚠️ This is an educational estimate, not a measurement. Never use it to decide whether to drive or operate machinery. Real BAC varies with food, metabolism, medication, and health. The only safe amount of alcohol before driving is none.
What this tool does
The Blood Alcohol Calculator estimates your Blood Alcohol Concentration — the percentage of alcohol in your bloodstream — using the Widmark formula. It factors in how much you drank, your body weight, your sex, and how long it’s been since you started drinking.
BAC is what legal limits and breathalysers actually measure, which is very different from simply counting drinks. The result includes a status band and a comparison against driving limits in India (0.03%), Scotland (0.05%), and the US and England (0.08%).
How BAC rises and falls
Alcohol enters your bloodstream as you drink and your body clears it at a roughly constant rate — about 0.015% per hour. Nothing reliably speeds that up: not coffee, not a cold shower, not eating after the fact. Only time lowers BAC. That’s why this tool subtracts elimination based on the hours since your first drink and estimates how long until you’d reach zero.
Important limits of this estimate
- It uses population-average ratios, so it won’t match any specific person exactly.
- It assumes drinks are spread across the time you entered, not all at once.
- It cannot account for food, medication, illness, tolerance, or genetics.
- It is not medical or legal advice. If you’re concerned about your drinking, talk to a doctor.
Privacy
Everything runs in your browser via the pure calculateBac function. Nothing you enter is uploaded or stored — you can verify this in your browser’s Network tab.