Transparent calculations
How CaffCalc works
CaffCalc estimates how caffeine falls over time. It can help you compare your options, but it can’t measure caffeine in your body or tell you how well you’ll sleep.
The formula
We work out what might remain from each drink at the time you choose, then add the amounts together. The tracker uses the same formula every 30 minutes. Change the half-life setting and the estimate changes too.
Why half-life is adjustable
People clear caffeine at different speeds. We start with a five-hour half-life, then show three-, five- and seven-hour examples so you can see how much the answer could vary.
Tracker dates and history
Your browser’s time zone decides which day a drink belongs to. Weekly totals describe what you logged on that device. They aren’t measurements of your body or targets to aim for.
What the thresholds mean
The 50, 25 and 10 mg times help you follow the curve. None is a proven safe level or a point where good sleep is guaranteed. For the coffee comparison, we use a general brewed-coffee example of 95 mg.
Limitations
- Absorption is treated as immediate.
- The model assumes exponential clearance at a constant rate.
- Drink caffeine values are estimates unless you enter a labelled dose.
- Pregnancy, medicines, smoking, genetics and health conditions may change clearance.
For medical or pregnancy-specific advice, speak to a qualified healthcare professional.