Caffeine Half-Life Calculator
How much caffeine is still in you, hour by hour — exponential decay made visible.
A 2 p.m. 200 mg coffee still has ~50 mg working at midnight on an average metabolism — caffeine blocks adenosine, the sleep-pressure molecule, which is why it delays deep sleep even when you fall asleep fine. Pregnancy stretches the half-life to 15+ hours by the third trimester; hormonal contraceptives roughly double it. Smoking halves it, which partly explains heavy-smoker coffee habits.
Formula
For general information only — not medical advice, a diagnosis or a treatment plan. Consult a qualified healthcare professional before making health, diet, medication or exercise decisions.
How much caffeine is still in you, hour by hour — exponential decay made visible. The Caffeine Half-Life Calculator is a free, private caffeine half life tool — every result computes instantly in your browser with no sign-up and no data upload.
About Caffeine Half-Life Calculator
A 2 p.m. It applies remaining = dose × 0.5^(hours ÷ half-life). Use the Caffeine Half-Life Calculator to get an instant, clearly-explained result with the working shown step by step — free, private and with the source method cited.
How to use Caffeine Half-Life Calculator
- 1Enter your details in the Caffeine Half-Life Calculator input fields above.
- 2The result updates instantly with the working and reference bands shown.
- 3Adjust any value to explore how it changes the outcome — it's free and unlimited.
Why use Caffeine Half-Life Calculator?
- ✓Instant caffeine half life result that recomputes as you type — no waiting, no page reloads
- ✓100% client-side: your health data never leaves your browser
- ✓Shows the actual formula and your numbers substituted in, so you can see exactly how the result is reached
- ✓Based on published, citable sources (Institute of Medicine 2001 — caffeine pharmacokinetics)
- ✓Free forever with no sign-up, account or app install
Frequently asked questions
How does the Caffeine Half-Life Calculator work?+
A 2 p.m. The calculation uses the formula: remaining = dose × 0.5^(hours ÷ half-life). Everything runs instantly in your browser as you type — your inputs are never uploaded.
Is the Caffeine Half-Life Calculator accurate, and what is it based on?+
The method is traceable to authoritative sources: Institute of Medicine 2001 — caffeine pharmacokinetics. Results are estimates — individual variation always applies, so treat the output as a well-grounded starting point.
Is the Caffeine Half-Life Calculator free and private?+
Yes. It's completely free with no sign-up, and all computation happens locally in your browser, so none of your health data ever leaves your device.
Can I use this for medical decisions?+
This tool is for general information only and is not medical advice. Always consult a qualified healthcare professional before making health decisions.
What can I use the Caffeine Half-Life Calculator for?+
It's commonly used for caffeine half life, caffeine in system, how long caffeine lasts. How much caffeine is still in you, hour by hour — exponential decay made visible.
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