About the AlcoCalc project

Why AlcoCalc was created

The project aims to help understand the amount of ethanol in beverages and the assumptions of its model degradation. The calculator shows the calculation transparently: used inputs, assumptions and time course. It does not replace a breathalyzer or professional assessment.

Inputs actually used by the calculation

Portion volume V in ml, alcohol content ABV in %, number of portions, weight m in kg, selected distribution model and start and end time of drinking. Specific brands have a default ABV; the label of a specific product takes precedence over the information in the catalog.

Amount of pure ethanol

A = Count × V × ABV / 100 × 0.789. The constant 0.789 g/ml is the approximate density of ethanol. For example, 500 ml at 5% is approximately 19.7 g of ethanol. This is the amount in the drink, not automatically the blood alcohol concentration (‰) in the blood.

Distribution coefficient r

The model dose is calculated as A / (m × r). The tool uses r = 0.68 for the male and 0.55 for the female model. These values ​​are also used in published eBAC models [1], but individual body composition may differ from the averages. They are not an individual measurement.

Degradation: fixed assumption 0.15 ‰ per hour

AlcoCalc subtracts 0.15 ‰ per hour from one common model level. Jones's review describes individual differences in blood elimination rates of approximately 0.1–0.3 g/l/h [2]. Therefore, one constant does not describe every person. The units g/l and mass blood alcohol concentration (‰) are generally not exactly the same; the tool uses a simplified model convention.

Absorption and distribution over time

Each drink is divided equally into 60 doses within the drinking range; each model is absorbed for 45 minutes. At zero interval length, it is one dose. These are the implementation prerequisites of AlcoCalc. Source [1] uses a different absorption assumption and does not validate our 45-minute setting.

Uncertainty and difference from reality

The publication Alcohol calculations and their uncertainty [3] explains the uncertainty of calculations based on Widmark's approach. An inaccurate volume, concentration, time or distribution factor will affect the result. AlcoCalc does not directly take into account food, medication, health status or individual metabolic rate. It does not provide a guaranteed deviation or a confidence interval.

Indicative and non-binding result

All values and times are indicative, informative and non-binding. They may differ significantly from the actual level and from the measurement. The tool does not provide a medical or legal assessment, has no legal probative value and does not confirm fitness to drive.

Not even 0.00 ‰ is a confirmation of sobriety

Zero, green color and smiley indicate the result of the model. The blood alcohol concentration value (‰) is rounded to two decimal places. Do not use a calculator, deduction or sense of sobriety to decide if you can drive.

Transparency and peer review

The project does not list fictional reviews, expert authors or certification. References to professional literature explain the principles used; do not imply endorsement or clinical validation of AlcoCalc. Before the public launch, the real operator and contact must be added and a professional review of the model must be ensured.

Expert resources

• [1] Prevalence of Hangover Resistance According to Two Methods for Calculating Estimated Blood Alcohol Concentration (eBAC), 2020 — Appendix A
• [2] A. W. Jones: Pharmacokinetics of Ethanol — Issues of Forensic Importance
• [3] Alcohol calculations and their uncertainty, 2015

The source publications support the stated principles, not the certification of this calculator.

Related topics

• Calculation methodology and assumptions
• Widmark's formula and calculation of blood alcohol concentration (‰)
• Using AlcoCalc safely
• Resources and documentation
• Data and Privacy