Health & Fitness
Caffeine Half-Life Calculator
Estimate how much caffeine remains in your system over time based on a 5-hour average half-life.
Preparing your result…
What this calculator does
Calculates Caffeine Half-Life Calculator using the formula verified against the cited source.
What your result means
An estimate from the inputs you enter, within the scope stated below — not advice.
Formula
Remaining caffeine = dose × 0.5^(hours elapsed ÷ half-life)
The step-by-step working for your own numbers appears with the result above and in the PDF report.
Frequently asked questions
Symbols and assumptions
- Inputs
- The values entered in the fields above
- • Illustrative first-order caffeine remainder=dose mg×2^(−hours since defined starting point/personal half-life hours). For multiple doses, add each dose’s modeled remainder using its own elapsed time.
Sources and review
Reviewed 2026-10-18 · Next review 2027-04-18
- • Half-life varies with pregnancy, smoking, medicines and liver function; input is an assumption unless measured. Absorption and active metabolites are not modeled. A calculated remaining dose does not determine sleep effects or a universally safe time for another dose.
Important limitation
This is an educational estimate based only on the values and formula shown. Verify current rates, rules, units, and professional standards before relying on the result. It is not personalized financial or investment advice.
Quick reference
| Scenario | Caffeine consumed (mg) | Personal half-life (hours) | Hours since consumption (hours) | Caffeine remaining |
|---|---|---|---|---|
| Worked example | 200 | 5 | 4 | 114.8698 mg |
| Half the amounts | 100 | 2.5 | 2 | 57.4349 mg |
| Double the amounts | 400 | 10 | 8 | 229.7397 mg |
Need the full picture? Get the detailed PDF report with charts, tables, formulas and working steps.
Reviewed 2026-10-18 · Next review 2027-04-18
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