BAC Estimator

Educational, simplified mass/volume Widmark-style model for fixed adult reference presets. It does not measure your BAC or determine safety or legal compliance.

Inputs and assumptions

Enter weight in kg or lb, elapsed hours since the first drink, and each drink’s volume in ml and alcohol by volume (ABV). One lb is 0.45359237 kg. Decimal commas and points are accepted. The 500 ml beer preset is not a US or imperial pint.

All alcohol is assumed absorbed and distributed at the start. Individual absorption, food, later drinks, body composition, medications and changing elimination rates are not modeled. Actual BAC may still rise after drinking stops. The reference presets are illustrative averages, not personalized biological measurements.

Formula and units

A = Σ(volume × ABV / 100 × 0.789) in grams. C = max(0, A / (r × mass) − 0.15 × hours) in g/L. This simplified model treats r = 0.68 or 0.55 as an assumed distribution volume in L/kg, not the original mass/mass Widmark factor. Ethanol density is approximated as 0.789 g/ml. Elimination is fixed at 0.15 g/L/h. The displayed % w/v is C / 10 (g per 100 ml); g/L is not labeled as mass-based promille (g/kg).

Example

330 ml at 5 % contains 13.0185 g ethanol. With the 0.68 L/kg preset and 75 kg, the model gives 0.2553 g/L at time zero and 0.1053 g/L after one hour.

Model times

Hours to level L = max(0, (C − L) / 0.15), assuming no further alcohol and the same fixed elimination rate. Levels 0, 0.8, 0.5 and 0.2 g/L are examples, not legal limits or driving advice. Zero means only that the model is at or below that level; it does not establish that alcohol is absent or that you are unimpaired.

Limits

Input limits (1–1000 kg, 0–10000 hours, 0–10000 ml per drink, ABV 0–100 %, at most 100 drinks) are software limits, not medically plausible ranges. No drinks produces an empty state, not a safety assessment. Drinks are not saved across navigation.

Never use this estimate or its model times to decide whether to drive.