dose (mg)had ithours ago
95 mgstill in your system
100%of initial dose
11.2huntil under 20mg
—negligible by
Average caffeine half-life is roughly five hours. People with a slow CYP1A2 variant — about half of us — can take 8-10. Pregnancy slows it further.
About this tool
How to use it
- Enter the caffeine dose in mg (a standard drip coffee is ~95 mg).
- Enter how many hours ago you had it.
- See how much is still in your system and when it drops below 20 mg.
Why it lives here
Everything runs in your browser. No account, no ads, no tracking, and no upload.