Caffeine Clearance Calculator
Wondering why that evening coffee keeps you awake? Enter how much caffeine you had and when bedtime is, to see exactly how much is still active in your body hour by hour — based on the 5-hour half-life.
How to use
- Enter the caffeine amount in milligrams.
- Enter how many hours pass between the drink and bedtime.
- See what remains each hour and at bedtime.
Note
Uses exponential decay with a 5-hour half-life: remaining = amount x 0.5^(hours/5). Half-life varies between people (roughly 3 to 7 hours) and is longer in pregnancy and with some medicines. Estimate only — not medical advice.
Frequently Asked Questions (FAQ)
How is remaining caffeine estimated?
With exponential decay using a 5-hour half-life: remaining equals amount times 0.5 raised to the power of hours divided by 5.
What does the result show?
The caffeine left each hour for 12 hours in a table, plus the amount still in your system at bedtime.
Is the 5-hour half-life the same for everyone?
No. It varies between people, roughly 3 to 7 hours, and is longer in pregnancy and with some medicines. This is an estimate only, not medical advice.
How can I use this to protect my sleep?
Enter your caffeine in milligrams and the hours until bedtime to see how much will still be active when you sleep, and move your last coffee earlier if the number is high.