Caffeine calculator

Estimate how much caffeine is still in your system — enter each dose in mg and hours ago, and see when it drops below a sleep threshold.

Caffeine halves roughly every 5 hours. Add what you drank and when, then see how much is still in your system and when it drops below a threshold.

Everything runs in this browser.

How to use

  1. Add each dose as caffeine in mg and how many hours ago you took it.
  2. Adjust the half-life and your sleep threshold (mg).
  3. Read the current amount and when it falls below the threshold.

What it supports

Up to 12 doses of 1–2,000 mg each, −72 to +72 h relative to now; half-life adjustable 1–24 h. A simple exponential-decay estimate — not medical advice; sensitivity, pregnancy, and medication change the picture.

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