Introducing the Blood Alcohol Calculator — A Widmark BAC Estimate

⚠️ Educational estimate only. This tool can never tell you whether you’re safe to drive. The only safe amount of alcohol before driving is none.

The new Blood Alcohol Calculator estimates Blood Alcohol Concentration — the number that legal limits and breathalysers are built around — using the classic Widmark formula.

What it does

• Estimates BAC from drinks, body weight, sex, and hours since drinking.
• Accounts for elimination over time at roughly 0.015% per hour.
• Adjustable drink size for US (14 g), UK (8 g), or custom servings.
• Compares limits for India (0.03%), Scotland (0.05%), and the US/England (0.08%).

Why we built it

BAC is widely misunderstood — it isn’t the same as counting drinks, and feeling sober isn’t the same as being sober. The calculator is here to build that understanding, not to grant permission. It uses population-average constants and can’t account for food, medication, or individual metabolism, which is exactly why it must never inform a decision to drive.

Try it

Use the Blood Alcohol Calculator to see how weight, sex, and time change BAC. For the formula, its assumptions, and its limits, read How the Widmark BAC Formula Works (and Its Limits). To track weekly intake instead, see the Alcohol Units Calculator.