Caffeine Cutoff Calculator
When should you have your last coffee, tea, or pre-workout? Add what you drink today, your bedtime, and a few details about you. The calculator estimates how much caffeine is still in your body at bedtime and gives you the latest time to finish each drink.
Optional: things that change how fast caffeine clears
These are well studied factors that slow down or speed up caffeine clearance. Everyone is different, so if any apply, it is worth asking your doctor about caffeine.
Coffee, tea, cola, and energy drink amounts are based on Mayo Clinic averages (cola and energy drink scaled to can size). Cold brew, matcha, pre-workout, and pills are common label amounts. Check the label when you can, since brands and cafes vary a lot.
Caffeine is absorbed over about 45 minutes, then your body clears it at a steady rate. For a typical healthy adult, half of it is gone in about 5 hours. That number, the half-life, ranges from about 2 to 10 hours between people.
We add up every drink you list and estimate how much caffeine will still be in your body at bedtime and in the two hours after. The goal is to stay under about 32 mg. We set that line so the results match a 2023 review of 24 studies by Gardiner and colleagues, which found people should finish a 107 mg coffee at least 8.8 hours before bed and a 217 mg pre-workout at least 13.2 hours before bed.
What changes the result:
- Pregnancy and birth control pills slow clearance a lot, so caffeine lasts much longer.
- Smoking speeds clearance up, so caffeine wears off sooner.
- Liver conditions can slow clearance a lot. Your doctor is the best guide here.
- Age: people in midlife and later tend to see more effect from caffeine on their sleep, so we use a lower line from age 50.
- Sex: on its own, it makes little difference to clearance. The big differences come from pregnancy and the pill.
- Your usual intake: regular drinkers get used to some effects of caffeine, but their bodies do not clear it much faster, and studies still see sleep changes in daily drinkers. So we only shift the line a little: a bit lower if you rarely have caffeine, a bit higher if you have a lot every day.
We show a typical time and a cautious time for people who clear caffeine slowly. Treat it as a range, not an exact answer. This is general education, not medical advice.
Sources
- Gardiner C, et al. The effect of caffeine on subsequent sleep: a systematic review and meta-analysis. Sleep Medicine Reviews, 2023. doi.org/10.1016/j.smrv.2023.101764
- Mayo Clinic. Caffeine content for coffee, tea, soda and more. mayoclinic.org
- U.S. FDA. Spilling the Beans: How Much Caffeine is Too Much? fda.gov
- USDA FoodData Central (coffee, espresso, tea). fdc.nal.usda.gov
- Abernethy DR, Todd EL. Impairment of caffeine clearance by chronic use of low-dose oestrogen-containing oral contraceptives. Eur J Clin Pharmacol, 1985.
- Knutti R, et al. Effect of pregnancy on the pharmacokinetics of caffeine. Eur J Clin Pharmacol, 1981.
- Parsons WD, Neims AH. Effect of smoking on caffeine clearance. Clin Pharmacol Ther, 1978.
- Statland BE, Demas TJ. Serum caffeine half-lives: healthy subjects vs. patients having alcoholic hepatic disease. Am J Clin Pathol, 1980.
- Drapeau C, et al. Challenging sleep in aging: the effects of 200 mg of caffeine during the evening in young and middle-aged moderate caffeine consumers. J Sleep Res, 2006.
- Weibel J, et al. Regular caffeine intake delays REM sleep promotion and attenuates sleep quality in healthy men. J Biol Rhythms, 2021.
- Blanchard J, Sawers SJ. Comparative pharmacokinetics of caffeine in young and elderly men. J Pharmacokinet Biopharm, 1983.
Knocked Sleep Support is a melatonin-free blend of magnesium glycinate, L-theanine, GABA, and apigenin, made to help you relax at bedtime.* See Sleep Support
*These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.
This calculator is for general education only and is not medical advice. If you are pregnant, nursing, take medication, or have a health condition, talk with your doctor about caffeine. The FDA cites 400 mg a day as an amount not generally linked with negative effects for healthy adults.