Caffeine cutoff calculator

Where the cutoff times come from

They come from a 2023 review in the journal Sleep Medicine Reviews that pooled 24 studies on caffeine and sleep. On average, caffeine cut total sleep by 45 minutes, made it take 9 minutes longer to fall asleep and reduced deep sleep by about 11 minutes.

The researchers then worked out how early each drink has to be to avoid losing sleep:

• Coffee (about 107 mg in a 250 mL cup): at least 8.8 hours before bed.
• A pre-workout supplement (about 217 mg a serve): at least 13.2 hours before bed.
• Black tea (about 47 mg a cup): no cutoff. A single cup didn't measurably cut sleep at any time of day.

With a 10:30 PM bedtime, that puts the last coffee at 1:42 PM and the last pre-workout at 9:18 AM. The study found that the later the caffeine, the more sleep it cost.

Why it's earlier than you'd think

Caffeine's half-life, the time it takes your body to clear half of it, is typically 3 to 6 hours. Going by that alone, an afternoon coffee would seem harmless by bedtime. The study's cutoffs land well before that, because even the caffeine left over at night still affected sleep.

People clear caffeine at very different speeds. The authors note the half-life can vary by up to 8 hours between healthy adults, and suggest treating the cutoffs as a starting point. If you sleep fine after an afternoon coffee, you may clear it fast. If you don't, try moving it earlier.

Check how much is in your drink

Caffeine varies a lot between drinks. According to the FDA, a 12 ounce cup of brewed coffee has about 113 to 247 mg, and most energy drinks have 54 to 328 mg in a 16 ounce can. A large coffee or a strong energy drink can be closer to the pre-workout row than the coffee row. The FDA cites 400 mg a day as an amount not generally linked to dangerous effects in healthy adults.

See whether it helps

The best test is your own sleep. Move your last coffee earlier for a couple of weeks and compare. Sleep Tiles scores every night your Apple Watch, Oura Ring, WHOOP or Garmin saves to Apple Health, so you can see whether the change shows up in your scores.

Questions

When should I stop drinking coffee before bed?

At least 8.8 hours before bed for a regular cup of about 107 mg, according to a 2023 review of 24 studies. With a 10:30 PM bedtime, that means by 1:42 PM.

Is tea OK in the evening?

The same review found no cutoff for a single cup of black tea, which has about 47 mg of caffeine. More cups, or stronger tea, add up.

How long does caffeine stay in your body?

Its half-life is typically 3 to 6 hours, so about half of it is still in your body 3 to 6 hours later. It varies a lot from person to person.

What about energy drinks?

They range from about 54 to 328 mg in a 16 ounce can, according to the FDA. Check the label. If it has around 200 mg or more, the pre-workout cutoff is the closer guide.