Half-life
Uses an average caffeine half-life of 5.7 hours.
Caffeine Half-life
Sleep Hygiene Analytics
Predict when caffeine leaves your system to plan for better sleep.
Internal Caffeine at Bedtime
44.5mg
Safe Sleep
안전권입니다. 카페인이 충분히 배출되어 쾌적한 수면을 기대할 수 있습니다.
For sleep, the caffeine left at bedtime can matter more than the cup count
This calculator estimates how much caffeine may remain at your target bedtime based on intake amount and time. It uses an average 5.7-hour caffeine half-life and flags bedtime residue above about 50 mg as more likely to interfere with sleep.
Calculation basics
Remaining amount
remaining = dose×0.5^(elapsed hours/5.7)
Bedtime threshold
About 50 mg remaining is treated as a possible alertness level.
How to use
- Enter the caffeine amount in milligrams.
- Choose intake time and target bedtime.
- Use the bedtime residue to adjust your personal caffeine cutoff.
Frequently asked questions
Is caffeine half-life the same for everyone?
No. Genetics, liver metabolism, pregnancy, medications, and smoking status can change caffeine clearance.
Does under 50 mg guarantee good sleep?
No. Sensitivity, stress, light exposure, and sleep habits also affect sleep quality.
Can I use this for energy drinks?
Yes if you know the caffeine amount in mg, though sugar and other ingredients may also affect alertness.
Results are general estimates and are not a substitute for professional medical advice about sleep problems or caffeine sensitivity.