Caffeine calculator
Enter a caffeine amount, when you drank it, a half-life, and a bedtime. The calculator uses the same exponential decay formula as Brewlytics: remaining = dose × 0.5^(hours ÷ half-life). Results are informational estimates, not a measurement of caffeine in your body.
Download for iPhoneA 200 mg drink at 2:00 PM with a 5-hour half-life has about 132 mg remaining at 5:00 PM (3 hours later) and about 57 mg remaining at 11:00 PM (9 hours later). It reaches 50 mg a little after 11:20 PM. Change the half-life and those times move.
Brewlytics Pro applies this half-life model to every logged drink, then adds the remaining amounts. The website calculator is for one drink at a time so you can inspect the assumption. The app keeps the running total from your actual log, widgets, and bedtime setting.
If the bedtime estimate is higher than you want, the practical levers are an earlier last drink, a smaller serving, or a longer gap before sleep. Individual sensitivity varies, and this page does not diagnose sleep or give medical advice.
Remaining caffeine = dose × 0.5^(hours elapsed ÷ half-life). That is an exponential decay model. Brewlytics uses the same formula in the iPhone app.
A common published average is about 5 hours, with a wide individual range. Brewlytics Pro lets you set a half-life so the estimate uses your chosen assumption. This calculator does not know your metabolism.
No. The result is an informational estimate from the numbers you enter. It does not measure caffeine in your body or predict sleep quality.