SafeBAC CalculatorInformational BAC Tool

How Accurate Are BAC Calculators?

There is no such thing as a perfectly accurate online BAC calculator. This page explains why—and how to interpret results safely.

What does “accurate” really mean for BAC?

For BAC, accuracy could mean how close an estimate is to a real blood or breath test at a given moment. Because online tools rely on self-reported drinks and generalized formulas, even a well-designed calculator can only approximate reality.

Key assumptions behind BAC estimates

Most calculators assume a fixed distribution ratio based on sex, a standard elimination rate per hour, and typical drink sizes and ABV. In practice, each of these can vary substantially from person to person and drink to drink.

Why calculators disagree with each other

Some tools ask for more detail about your drinks, while others use a rough drink count. Formulas, rounding, and reference values also differ. Two tools can both be reasonable yet produce slightly different numbers from the same inputs.

Using estimates safely

The safest way to use any BAC calculator is as a rough educational guide only. Treat higher estimates as warnings and never treat lower estimates as guarantees that you are safe or legal to drive.

Accuracy FAQ

No online BAC calculator can guarantee accuracy. Our goal is to be transparent about assumptions and biased toward safety, not to claim perfect precision.
Consumer devices can use different sensors, algorithms, and calibration standards. Some may estimate impairment rather than actual BAC. Always treat such readings as rough and never as a license to drive.
Sometimes they can be in the same range, but differences of several hundredths of a percent or more are possible. Only properly used, calibrated professional equipment can measure BAC reliably.
BAC CalculatorTime to Zero