Blood Alcohol Range Calculator
Turns drinks into grams of pure alcohol and runs an optional simplified Widmark-type formula on parameters you supply. Educational only — not a BAC reading or driving guide.
This does not measure blood alcohol and cannot tell you whether you can drive.
It turns drinks into grams of pure alcohol and, if you choose, runs a simplified textbook formula with numbers you supply. Food, drinking pattern, health and medication change real blood alcohol. If you have been drinking, do not drive.
Inputs
Grams of pure alcohol from your drinks, plus an optional what-if scenario using parameters you supply. Educational — never a driving decision.
Enter the values and press Calculate.
Or load an example to see a worked result.
Before you rely on this: Safety-critical: treat this as a preliminary check only. Always verify against the governing standards and have a competent person review the result before use.
How to use this calculator
- Enter the alcohol as Australian standard drinks (10 g each), as a drink volume and % ABV, or directly in grams. Another country's definition can be entered as grams per drink.
- That gives the dose. To explore the textbook formula, also enter body mass, a body-water factor r, an elimination rate β and the hours since drinking began — none are filled in for you. A second r and β show how sensitive the arithmetic is.
- Press Calculate and read the dose, the scenario table and the assumptions. The result is educational arithmetic, never a reading of your blood alcohol.
How it works
Dose: A (g) = standard drinks × grams per drink, or volume (mL) × ABV ÷ 100 × 0.789 g/mL (ethanol density near 20 °C).
Simplified post-absorption (Widmark-type) formula: BAC (g/dL, %) = max(0, A ÷ (r × m × 10) − β × t), with m in kg and t in hours. With two values of r and β the tool shows the minimum and maximum over those scenarios — a sensitivity range, not a probability or confidence interval.
Real blood alcohol depends on food, drinking pattern, health, medication and individual physiology. A zero from the formula means only that it has run out of dose to eliminate — not that anyone is sober — and nothing here indicates when it is safe or legal to drive.
Worked example
5 Australian standard drinks, and a synthetic test scenario. 5 × 10 g = 50 g of pure alcohol. As an arithmetic check only (not a recommended physiological scenario): A = 50 g, m = 80 kg, r = 0.7, β = 0.015 g/dL per hour, t = 3 h gives 50 ÷ (0.7 × 80 × 10) − 0.015 × 3 = 0.0893 − 0.045 = 0.04429 g/dL.
Tips
- If you have consumed alcohol, the safest choice is not to drive — plan ahead and use a safe ride.
- Standard drink sizes differ between countries; check the label for the number of standard drinks in a container.
Frequently asked questions
Does this measure BAC?
No. It converts drinks to grams and runs a simplified formula on numbers you choose. Only an approved breath or blood test measures alcohol.
Why is the range not a confidence interval?
It is just the lowest and highest result across the parameter values you entered. It says nothing about how likely any value is, and real results can fall outside it.
Can it tell me when to drive?
No. It gives no driving, legal-limit or time-until-sober answer and should not be used for that decision. If you have been drinking, do not drive.
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Cite this tool
Zerdly. (2026). Blood Alcohol Range Calculator. Retrieved from https://www.zerdly.com/tools/blood-alcohol-range-calculator/
Tip: Enter any known values to calculate the remaining results.
Designed to run locally in your browser. Tool inputs are not intentionally stored by Zerdly unless stated otherwise.