🍷 BAC Calculator & Breathalyzer Science
Online Breathalyzer & BAC Calculator
Estimate your Blood Alcohol Content (BAC) and time to sobriety using the scientific Widmark formula, and learn how clinical breathalyzer tests actually work.
BAC Estimation Inputs
Calculated using the validated Widmark alcohol metabolism equation.
Estimated Blood Alcohol Content
Mild Impairment / Relaxation
Based on average hepatic clearance rate of ~0.015% BAC per hour.
🚨 Zero-Tolerance Safety Notice:
This tool is an informational mathematical approximation only. Individual metabolism varies by stomach fullness, medications, liver health, and genetics. Never use this calculator to decide if you are fit to drive. If you drank, call a taxi or rideshare.
Can You Actually Take an Alcohol Breath Test Online?
The short answer is NO. No smartphone, browser, or website can physically analyze your breath for alcohol. Any website or mobile app claiming to turn your phone's microphone or screen into an alcohol breathalyzer is fraudulent.
To measure alcohol in breath, you need specialized hardware: either a fuel-cell sensor (the gold standard used by police) or a semiconductor oxide sensor (used in personal keychain breathalyzers).
How Real Breathalyzers Work
When you consume alcohol, it is absorbed through the stomach and small intestine into the bloodstream. As blood flows through the pulmonary capillaries in your lungs, volatile ethanol diffuses across the microscopic alveolar membranes into the air sacs.
The scientific constant governing breath tests is Henry's Law, yielding a clinical 2,100:1 partition ratio: 2,100 milliliters of alveolar breath contain approximately the same quantity of alcohol as 1 milliliter of blood. Real breathalyzers require you to blow deeply for 5 to 7 seconds to sample this deep lung air.
The Widmark Formula Explained
Formulated by Swedish physician E.M.P. Widmark: BAC = [Alcohol in grams / (Body weight in grams × r)] - (β × Time in hours)
Where r is the gender body water constant (0.68 for men, 0.55 for women) and β is average metabolic decay (~0.015% per hour).
Looking for Lung Capacity Tests?
If you arrived here looking to check your lung fitness or breath-holding stamina rather than alcohol, explore our free breath-hold timer and lung capacity calculator.