Caffeine Cutoff Calculator
Tell us when you go to bed, what you drink and how fast you clear caffeine. We show the latest time for your last cup, and how much caffeine is still in your system at bedtime.
–
latest time for your last coffee
–hours before bed
–caffeine in the cup
–left if drunk at 3:00 PM
A 9 hour gap is a safe default for most adults. Use the calculator above to tune it to your own sensitivity.
How many hours before bed should I stop drinking coffee?
Most people should stop 8 to 10 hours before bed. A 2013 sleep study found 400 mg of caffeine taken even 6 hours before bed cut sleep by more than an hour. Slow metabolizers and light sleepers may need 10 hours or more.
What is the half-life of caffeine?
Caffeine has a half-life of about 5 hours in healthy adults, with a normal range of roughly 3 to 7 hours. Every half-life, half of the caffeine is cleared. A 100 mg cup is still about 50 mg after 5 hours and 25 mg after 10 hours.
Does caffeine half-life change from person to person?
Yes. Smoking can shorten it to about 3 hours, while pregnancy, oral contraceptives and some liver conditions can stretch it to 10 hours or more. Genetics (the CYP1A2 gene) also play a big role.
How much caffeine at bedtime is too much?
There is no single safe number, but many sleep researchers aim for under about 25 mg in the body at bedtime, roughly a quarter of a cup of drip coffee. This calculator lets you pick your own target.
Does decaf coffee count?
Decaf still has 2 to 15 mg per cup, so a cup late in the day is usually fine. See our explainer on how much caffeine is in decaf coffee for the details.