Caffeine cutoff calculator

Have your last cup of coffee at least 8.8 hours before bed. For a pre-workout drink, make it 13.2 hours, and for a big coffee-shop coffee, which can hold even more caffeine, at least that. Put in your bedtime and your drink below and we'll give you the clock time, plus how much caffeine will be left when you lie down.

Where the 8.8 and 13.2 hours come from

The 8.8-hour and 13.2-hour cutoffs come from a 2023 review of 24 small lab studies in healthy adults aged 18 to 65, most of them young men without sleep problems. In those studies, where doses were often large and usually close to bedtime, caffeine cost about 45 minutes of sleep on average.

The authors then worked out how close to bed two common doses could be taken before the loss of sleep showed up clearly in their data. Coffee with 107 mg needed 8.8 hours, and a pre-workout drink with 217 mg needed 13.2. Even at those times their model still points to a small loss, so treat them as the least.

Those are the only two times the review gives. Anything in between gets a straight line from one to the other, so those times are our estimate, and if anything they run a few minutes short. Smaller drinks get 8.8 hours too. The review couldn't show any loss of sleep from a cup of black tea (47 mg) at any hour, but its data were thin, and that isn't the same as no effect.

How much is left at bedtime

In most healthy adults it takes 3 to 7 hours for half the caffeine in a drink to clear, a stretch known as its half-life, and in some people it's as quick as 2 hours or as slow as 10. We use 5 hours, the middle of the usual range, for the main figure and show the 3-to-7-hour range next to it. The figure counts one drink, so anything left from earlier cups comes on top.

Some people clear it much more slowly. Pregnancy, birth control pills, liver disease and some medicines all lengthen the half-life, so if one of those applies to you, your cutoff is probably earlier than the one shown. A pharmacist can tell you whether a medicine you take slows caffeine down, and if you're pregnant, your doctor or midwife can give you a sensible daily amount.

What the times don't cover

The studies looked only at night sleep, so if you sleep in the day after a night shift, take these times as a rough guess. A late coffee that doesn't stop you falling asleep can still mean more time awake later in the night and a little less deep sleep. Our caffeine cutoff guide has typical amounts for common drinks, and how to cut back without a headache.

If you need caffeine to get through the day, or you doze off without meaning to, that's worth raising with a doctor. If you're drowsy, don't drive.

How Goodmorrow coaches it

Goodmorrow's caffeine habit is "No caffeine after 2pm," about right for a cup of coffee and an 11pm bedtime. Every day of the first week, a reminder comes at 1:30 with a line like "2pm cutoff soon. Anything after can be decaf." You check off the days you keep it, and at two weeks we'll say whether your nights look any different.