Real-Time Caffeine Buildup Calculator Manually log caffeine and see the half-life decay curve before bedtime
Step 1: Add a manual intake record
This is a manual log, not a background tracker. Once the page is closed, it cannot keep monitoring you; add a record after each drink.
1 means one default serving; use 0.5 or 1.5 for a half cup or a large drink.
Default is 5 hours; real values vary widely by metabolism, medication, age and genetics.
Default 50 mg is only a general reference, not a safety or medical line.
Current estimate
Estimated with Σ dose × 0.5^((now−intake time)/half-life).
Below the common adult 400 mg/day reference limit.
Uses 50 mg as a bedtime remaining-caffeine reference line.
Records are stored only in this browser's localStorage. They may disappear if you switch devices, clear data, or use private browsing.
Next 24 hours caffeine decay curve
The curve uses only the records you manually entered and the half-life setting; it cannot know about drinks you did not log.
Today's records
Honest disclaimer and health notes
- A common adult reference limit is about 400 mg/day (FDA/EFSA), but individual tolerance varies greatly.
- This tool is for manual logging and general information only. It is not medical advice and cannot diagnose sleep, anxiety, or cardiovascular issues.
- Pregnancy, trying to conceive, breastfeeding, teens, arrhythmia, medication use, or caffeine sensitivity may require different limits; follow medical or local official guidance.
Real-Time Caffeine Buildup Calculator
This tool is a manual intake log plus a decay curve, not an always-on background tracker. Add each coffee, tea, energy drink, cola or custom caffeine dose yourself; a static page cannot continue tracking after it is closed.
Caffeine half-life / 咖啡因半衰期
Caffeine half-life is commonly discussed in hours and varies widely; the default here is 5 hours. A common adult daily reference is about 400mg, but pregnancy, medication and sensitivity change the picture. Read more: Wikipedia: Caffeine、FDA caffeine guidance、EFSA caffeine topic
How the 24-hour decay curve works
The calculator uses remaining = Σ dose × 0.5^((t−intakeTime)/halfLife) for the records you manually enter. The dashed line is a bedtime reference threshold, defaulting to about 50 mg. It is a planning aid, not a medical safety line, and it cannot include drinks you forgot to record.
Privacy and related tools
Records stay in this browser's localStorage only and may disappear if you clear browser data or change devices. You can also compare food and drink context with English Food Calories tool.
Important disclaimer
This is not medical advice. Pregnancy, breastfeeding, teens, heart rhythm issues, anxiety sensitivity, liver conditions, and medication interactions may require different caffeine limits; follow a qualified clinician or your local official guidance.