Slumber Studios

Free sleep tool

Caffeine Cutoff Calculator

Enter your bedtime and see when to switch to decaf, based on how long caffeine actually lingers in the body.

I want to be asleep by

My usual drink is (optional)

Why a window instead of a time

The six-hour end is the one figure that comes from a direct measurement. In a controlled trial, 400 mg of caffeine disrupted sleep when taken at bedtime, three hours before bed, and six hours before bed. Every timing tested caused measurable disruption, which makes six hours the latest defensible cutoff rather than a safe one — the study never found a timing that came back clean.

The other end of the window exists because people clear caffeine at very different rates. The half-life in an average adult is about five hours, but smoking roughly halves it, and liver conditions, CYP1A2 inhibitors and pregnancy stretch it well past the average. Oral contraceptives are one of the larger measured effects: one study found a half-life of 10.7 hours in women taking them against 6.2 hours in those who were not.

Ten hours is where this tool puts the cautious end, and it is worth being clear that no trial has tested that cutoff. It is the measured six-hour floor carried out across the slow end of the half-life spread: an extrapolation, not a finding. If you know you are slow to clear caffeine, it is the end to work from.

Caffeine content varies as much as people do, which is why every drink here is a range rather than a number. Brew strength, cup size and roast move the figures well beyond even those ranges, so treat them as a rough guide rather than a dose.

Questions

When should I cut off caffeine before bed?
The window this calculator gives runs from ten to six hours before your bedtime. The six-hour end rests on a trial in which 400 mg of caffeine, taken at bedtime, three hours before bed, and six hours before bed, disrupted sleep at every timing, making six hours the latest cutoff with evidence behind it. The ten-hour end adds a margin for bodies that hold onto caffeine longer.
What time should my last coffee be if I go to bed at 11 PM?
For an 11:00 PM bedtime, the last cup lands between 1:00 PM and 5:00 PM. Five o’clock is six hours ahead of that bedtime, the latest timing the trial behind this tool supports; one o’clock stretches the gap to ten hours for anyone who clears caffeine slowly. Enter your own bedtime, exact to the minute if you like, and the calculator moves the same window to fit it.
Why doesn’t picking a stronger drink change the cutoff time?
The trial that produced the six-hour figure used one dose, so there is no measured basis for sliding the cutoff up or down by the caffeine in a particular cup. What the drink picker does is personalize the explanation: it estimates how many milligrams would still be circulating at bedtime after one serving at the later cutoff, across average and slow clearance rates. Bigger doses leave more behind, which makes the case for the earlier end of the window.
How long does caffeine take to leave your system?
An average adult clears half of a caffeine dose in about five hours, and the remainder keeps halving from there. That rate varies a lot between people: smoking roughly halves the half-life, while pregnancy, liver conditions, certain medications, and oral contraceptives slow it down; one study measured 10.7 hours in women taking oral contraceptives against 6.2 hours in women who were not. The calculator publishes a window because of that spread.
Is 10 hours before bed a proven caffeine cutoff?
No trial has tested a ten-hour cutoff, and this page marks the figure as derived for that reason. It takes the measured six-hour floor and extends it across the slow end of the half-life range. That makes it the cautious end of the window: the end to plan from if caffeine tends to stay with you into the night, and an estimate either way.
Does decaf coffee still count against the cutoff?
Decaf is not caffeine-free, but it is close: USDA’s figure works out to about 2 mg in an 8 oz cup, against 80 to 100 mg for the same cup brewed regular. On the average five-hour half-life, a dose that small leaves next to nothing by bedtime, even for slow clearers. The other two additions carry real amounts. Instant coffee holds about 62 mg per cup, close to brewed, and dark chocolate somewhere between 12 and 24 mg per ounce depending on how dark it is, so both belong inside the same window as everything else on the list.

Where these numbers come from

The figures and links below were last checked against their sources on August 16, 2026.

This is general information, not medical advice. Sleep that stays bad for weeks is worth taking to a doctor.

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