// tool 02 · timing
Caffeine Sleep Cutoff Calculator
Tell it your bedtime and what you're drinking — it works backward from the same decay math to tell you the latest time you can have it without it still being active when you sleep.
This targets the same ~50mg "sleep-friendly" line used in the Half-Life Calculator. Sensitive sleepers may want a bigger buffer.
What is a caffeine cutoff time?
Your cutoff time is the latest point in the day you can realistically have caffeine and still have it decay to a low, sleep-friendly level by the time you go to bed. It depends on three things: how much caffeine you're having, your own half-life (how fast your body clears it), and what time you actually go to sleep.
A flat rule like "no coffee after 2pm" ignores all of that — a small green tea at 4pm is very different from a cold brew at 4pm. This calculator works it out properly for your specific drink and bedtime.
How this calculator works
It uses the same decay formula as the Half-Life Calculator, solved in reverse:
Cutoff time = Bedtime − (half-life × log₂(dose ÷ 50))
In plain terms: it figures out how many hours your chosen dose needs to decay down to ~50mg, then counts that many hours back from your bedtime. If your dose is already under 50mg, timing barely matters — there's nothing left to clear.
Recommended cutoff by drink (average metabolism)
| Drink | Amount | Cutoff before bedtime |
|---|---|---|
| Monster energy | ~160mg | ~8.5 hrs before |
| Cold brew coffee | ~155mg | ~8 hrs before |
| Brewed coffee | ~95mg | ~4.5 hrs before |
| Sting / generic energy drink | ~92mg | ~4.5 hrs before |
| Red Bull | ~80mg | ~3.5 hrs before |
| Latte / Cappuccino | ~77mg | ~3 hrs before |
| Matcha | ~70mg | ~2.5 hrs before |
| Espresso | ~63mg | ~1.5 hrs before |
| Instant coffee | ~62mg | ~1.5 hrs before |
| Black tea | ~47mg | Anytime |
| Chai tea with milk | ~40mg | Anytime |
| Cola soda | ~34mg | Anytime |
| Green tea | ~28mg | Anytime |
| Dark chocolate | ~24mg | Anytime |
Frequently asked questions
Why not just avoid caffeine after a fixed time, like 2pm?
Because a fixed cutoff ignores dose and your personal half-life. A double espresso and a green tea don't need the same cutoff — and someone with a slow metabolism needs an earlier one than someone with a fast one.
What if I'm not sure about my metabolism speed?
"Average" is a safe default for most healthy adults. If caffeine reliably keeps you up even from morning cups, try "Slow" for a more conservative cutoff.
Does this account for more than one drink?
This calculates one drink against one bedtime. For a full day with multiple drinks stacking on top of each other, use the Daily Caffeine Tracker.