STIMTRACE / METHODOLOGY
Transparent by design.
StimTrace is an educational model, not a blood measurement or medical recommendation. This page documents every important assumption behind the calculator.
The caffeine model
Every intake is treated independently using first-order exponential decay. The remaining amounts are then added together at each point on the timeline.
The default five-hour half-life is a practical population-level estimate. Real clearance varies with pregnancy, medication, smoking, liver function, age, and genetics. The adjustable range is intended for exploration—not self-diagnosis.
The comparison marker
The marker is a personal reference line. It is not a validated “sleep-safe” concentration. EFSA notes that even 100 mg close to bedtime may affect sleep in some adults, while individual responses vary substantially. StimTrace therefore lets you choose the marker and describes it as a comparison rather than a safety threshold.
Drink estimates
Regional presets use typical serving sizes and category averages informed by EFSA and FDA guidance. Branded Coca-Cola presets use Coca-Cola's published regional can sizes and caffeine figures; caffeine-free products are recorded as zero. Coffee preparation, bean, brand, and serving size can change caffeine considerably. When a product label is available, create a custom drink and use that value.
Chocolate and theobromine
Chocolate values use a 75% cocoa baseline and scale proportionally with the selected cocoa percentage. Real recipes do not scale perfectly, so this remains approximate. Theobromine uses a 7.2-hour half-life reported in a small comparative pharmacokinetic study. The combined curve uses an A₁ receptor-affinity mass ratio; it is explicitly not a validated stimulant conversion.
Sources
- European Food Safety Authority: caffeine assessment and typical servings
- U.S. FDA: typical caffeine ranges and variability
- Coca-Cola: caffeine in Original, Zero Sugar, and Light
- Coca-Cola Germany: regional products and package sizes
- Coca-Cola Great Britain: Coke and Diet Coke caffeine
- Coca-Cola U.S.: Coke, Diet Coke, and caffeine-free products
- Coca-Cola U.S.: Cherry and Vanilla Coke sizes and caffeine
- Drake et al.: caffeine 0, 3, or 6 hours before bedtime
- Lelo et al.: comparative caffeine and theobromine pharmacokinetics
- Review of adenosine-receptor antagonist affinities
- USDA FoodData Central: dark-chocolate nutrient data
Privacy
Your calculator timeline, favorites, settings, feedback draft, and history are stored in this browser. They are not included in analytics events. Optional written feedback is sent only when you deliberately open and send an email.