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Health Calculators

Caffeine Half Life Calculator

Verified formula Updated Jun 2026 Private — runs on your device

Enter details
mg
Verified formula Private

Caffeine remaining

100.0

For general information only — not financial, tax, legal or medical advice. Verify before you rely on it.

How to use the Caffeine Half Life Calculator

The Caffeine Half Life Calculator works out your caffeine remaining in an instant. Enter caffeine consumed and hours since consumed and the result updates as you type — it is free, needs no sign-up, and runs entirely in your browser so your figures stay private.

  1. Enter the caffeine consumed.
  2. Enter the hours since consumed.
  3. Read off your caffeine remaining — the calculator updates automatically, with no button to press.

Formula

The Caffeine Half Life Calculator uses the formula:

Caffeine remaining = Caffeine consumed × (0.5)^(Hours since consumed ÷ 5)

Worked example

For example, with caffeine consumed of 200 mg and hours since consumed of 5, the caffeine remaining is 100.0.

Inputs used
Caffeine consumed 200 mg
Hours since consumed 5
Results
Caffeine remaining 100.0

Results are estimates for educational use, not professional advice.

Frequently asked questions

Caffeine has a half-life of about 5 hours, so 200 mg drops to about 100 mg after 5 hours and 50 mg after 10.

It halves every 5 hours: remaining = dose × (½)^(hours ÷ 5).

Because it lingers for hours, caffeine late in the day can still be active at bedtime and disrupt sleep.

Yes. Pregnancy, some medications and genetics can lengthen it, while smoking can shorten it. 5 hours is a typical average.

Enter the caffeine consumed. Enter the hours since consumed. Read off your caffeine remaining — the calculator updates automatically, with no button to press.

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