Caffeine Cutoff Calculator
Find out the exact time to stop drinking coffee so it won't wreck your sleep after your shift.
Most people fall here. Half-life around 5 hours.
Why this matters
Caffeine has a half-life of 4–6 hours. That means if you drink a coffee at 4am, half of it is still working in your body at 9am — and a quarter is still there at 2pm.
For shift workers, this is brutal. Your "morning" coffee might be at 9pm. Your "afternoon" pick-me-up might be at 3am. By the time you're trying to sleep after your shift, you've got residual caffeine fighting your melatonin. That's why so many shift workers can't fall asleep even when they're exhausted.
The math is simple: stop caffeine at least 2 half-lives before bed, so it drops to roughly 25% by the time your head hits the pillow.
Pre-shift strategy that works
- Front-load your caffeine. Best coffee = 30 min before shift starts. You'll be sharpest 60–90 min in.
- Second cup, not third. A second coffee 3–4 hours in is fine. A third one past your cutoff is a bad trade.
- Replace late-shift coffee with cold water. Dehydration mimics fatigue. Cold water on the face + 500ml of water beats another espresso for the last 3 hours.
- Save the strong stuff for your hardest shifts. If you drink a triple every shift, you build tolerance fast.
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