How BAC Is Estimated
This calculator uses the Widmark formula, a standard method that factors in total alcohol consumed, body weight, biological sex (which affects body water percentage and thus alcohol distribution), and time elapsed since drinking began.
The body eliminates alcohol at an average rate of approximately 0.015% BAC per hour — this rate is relatively consistent and isn't meaningfully sped up by coffee, cold showers, or exercise, despite common myths.
Why This Is Only an Estimate
Actual BAC varies based on factors this calculator cannot measure: food consumption, medications, individual metabolism, hydration, and overall health. Impairment can also occur well below the legal limit — judgment and reaction time are affected starting at very low BAC levels.
Frequently Asked Questions
In all US states, the legal limit for drivers 21+ is 0.08% BAC. Commercial drivers face a stricter 0.04% limit. Drivers under 21 face zero-tolerance laws, typically 0.00-0.02% depending on the state.
The body metabolizes alcohol at approximately 0.015% per hour. A BAC of 0.08% takes roughly 5-6 hours to fully clear. This rate is relatively fixed and not meaningfully accelerated by coffee or other common myths.
No. This is an educational estimate only and should never be used to decide whether it's safe to drive. Many factors affect actual impairment that this tool cannot measure. Always choose a sober ride if you've been drinking.