A curve, but simplified
- Show a BAC curve over time
- Apply the Widmark formula once per drink
- Assume each drink is consumed instantly
- Don't adjust for whether you've eaten recently
Curve shown · instant drinks · fixed absorption
Many BAC apps plot a curve over time, but still assume you finished each drink instantly and don't adjust for whether you've eaten. Calcohol models how alcohol is absorbed and eliminated minute by minute — including how long it takes you to finish a beer, wine, or cocktail, and whether food is slowing absorption — updating your estimate every minute.
What sets Calcohol apart from other drink-tracking apps is realism. Many Widmark-based apps do show a BAC curve over time, but they still treat each drink as if you downed it in one gulp and use the same absorption timing whether or not you've eaten. In practice, a 12 oz beer might take five minutes — or an hour — to finish, and food can double the time to peak. Calcohol runs a full pharmacokinetic simulation minute by minute, distributing alcohol intake across your actual drinking duration and adjusting for fed vs. empty stomach.
In practice, your BAC rises gradually as alcohol enters your bloodstream, plateaus, then falls over several hours. A typical app's curve can look plausible but still be wrong — especially when it assumes a full pint of beer hits your system the moment you log it, or uses the same absorption rate after dinner as on an empty stomach. Calcohol's model accounts for when you drank, how long you took to finish each drink, whether you'd eaten, and how earlier drinks are still being processed — giving you a far more accurate picture of where you actually are, not just a projected peak.
Log a drink in seconds and watch your BAC curve evolve — rising as alcohol absorbs, falling as your body metabolizes it.
Record ABV, size in ounces, drink type, timing, and whether you've eaten. Presets for beer, wine, shots, and cocktails get you started fast.
The core differentiator: a live BAC curve that models drink duration, fed vs. empty stomach absorption, and elimination over time. See where you are now, when you'll peak, and when you'll be back to zero.
Your profile and drink history are stored locally on your device. Nothing is uploaded to a server.
Many apps use the Widmark equation to plot a BAC curve over time, but still assume instant consumption and a fixed absorption rate regardless of food intake. Calcohol goes further with a full time-based simulation: BMI-adjusted body-water distribution, alcohol spread across drink duration, fed vs. empty stomach absorption timing, and first-order elimination. Those details are what make real-world estimates meaningfully more accurate.
Widmark equation with BMI-adjusted distribution factor
Linear rise over time, adjusted for food intake
Constant rate with a short post-absorption delay
All drinks combined into a single BAC curve
For each minute of alcohol intake, Calcohol computes a peak BAC using a variant of the Widmark formula. Pure ethanol mass is derived from drink volume and ABV, then distributed across total body water using a sex- and BMI-adjusted Widmark factor (r).
Where oz is fluid ounces consumed, ABV is alcohol by volume (%), and mass is body weight in kilograms. The constant 23.33073 converts fluid ounces of ethanol to grams (29.5735 mL/oz × 0.789 g/mL). Dividing by 10 converts the result to the standard BAC decimal scale (e.g., 0.080).
Rather than fixed sex-specific constants, Calcohol uses regression equations that adjust the Widmark factor r based on body mass index. Higher BMI generally corresponds to a lower distribution factor (more body mass, less relative water).
| Parameter | Value | Source |
|---|---|---|
| Male intercept | 1.0181 | Kwan et al., 2014 |
| Male BMI slope | −0.01213 | Kwan et al., 2014 |
| Female intercept | 0.9367 | Kwan et al., 2014 |
| Female BMI slope | −0.01240 | Kwan et al., 2014 |
Alcohol does not enter the bloodstream instantly. Calcohol models a delay before absorption begins, then spreads each drink's contribution linearly until peak BAC is reached. Whether you've eaten significantly affects how quickly alcohol is absorbed.
| Parameter | Value | Notes |
|---|---|---|
| Absorption delay | 10 min | Before BAC begins rising |
| Time to peak (empty stomach) | 45 min | Faster gastric emptying |
| Time to peak (fed) | 90 min | Delayed by food intake |
This is a key limitation of most Widmark-based apps: even when they plot a curve over time, they usually treat the full drink dose as entering your bloodstream at once and don't adjust time-to-peak for whether you've eaten. Calcohol instead estimates consumption duration from drink size and timing. Shots (< 2 oz) are treated as instant. Longer drinks are spread across their logged duration, or inferred from the gap to the next drink — so a beer sipped over 45 minutes after a meal produces a very different curve than one logged as finished immediately on an empty stomach.
Once alcohol is absorbed, it is removed from the bloodstream at a roughly constant rate — a well-established approximation known as zero-order or linear elimination in many BAC models. Calcohol applies a short delay between absorption and the start of measurable elimination.
| Parameter | Value | Notes |
|---|---|---|
| Elimination rate | 0.015 BAC/hr | ≈ 0.00025 BAC/min |
| Elimination delay | 15 min | Post-absorption lag |
The 0.015/hr rate is a widely cited population average for alcohol metabolism. Individual rates vary substantially based on genetics, liver function, and other factors. The 15-minute elimination delay is an empirical tuning parameter that correlates well with observed data but does not have a dedicated formal study.
Each logged drink contributes its own absorption curve. Contributions are summed minute-by-minute to produce a single BAC timeline. Elimination is applied globally across the combined curve, with a rolling window that tracks how much alcohol entered the bloodstream in each prior minute.
For consumption statistics, Calcohol converts logged drinks to U.S. standard drink equivalents using 0.6 fluid ounces of pure ethanol per standard drink.
Calcohol's model draws on published research in alcohol pharmacokinetics. Links open on NCBI PubMed Central.
BMI-adjusted Widmark factor regression equations for males and females. PMC4361698
Gastric emptying and alcohol absorption timing — informs absorption offset and time-to-peak parameters. PMC4112772
Pharmacokinetic modeling of blood alcohol curves — used to informally validate elimination delay behavior. PMC3400212
Original formulation relating ingested alcohol dose to blood concentration via body water distribution. Foundational reference for all Widmark-based BAC estimators.