When should I stop drinking coffee?
It depends on the cup more than the clock. Put in your drinks and when you fall asleep, and drag them along the day to see what's still in you when your head hits the pillow.
When you fall asleep at 11:00pm
83 mgA measured cost
You'll fall asleep with about a cup of coffee in you.
39 to 101 mg if your half-life is 3 to 6 hours. About 48 mg at 3am.
- 95 mg
190 mg
Half-life: 5 hours, the average. Set yours
Your last drink, a 16 oz coffee at 3:00pm
- Under 40 mg at sleep
- by 8:10am
- Under 80 mg
- by 2:45pm
A measured cost Over our 80 mg line. 400 mg taken 12 hours before bed leaves about 84 mg and still cut about 21 minutes of deep sleep. The 40 and 80 mg lines are ours.
What your result means
- Low, under 40 mg: nothing to change. The 2023 review's cutoffs for a coffee and a pre-workout both leave about this much at bedtime.
- In between, 40 to 80 mg: one trial found nothing at this level and another found less deep sleep a little above it. If you wake up tired, move your last drink an hour or two earlier, or tap the smaller drink.
- A measured cost, over 80 mg: move the big drink to the morning or swap it for a small one. In a 2025 trial, 400 mg taken 12 hours before bed left about 84 mg and still cut about 21 minutes of deep sleep.
- No time today: your earlier drinks already leave too much at bedtime, so the afternoon ones are the place to start. Make them smaller before you move the morning cup.
What to do next
- Keep one change for a week, the earlier time or the smaller drink, whichever is easier to stick to.
- Compare two weeks. One as you are now and one with the change. On a ring or watch, look at deep sleep and time awake in the night. Without one, write down each morning how long you took to fall asleep and how rested you feel from 1 to 5.
- On the pill, pregnant or a smoker? Set your half-life first, since each one moves your cutoff by hours.
The latest time for each drink
For one drink and nothing else that day, on a 5 hour half-life, the latest time that leaves under 40 mg when you fall asleep. Never later than 4 hours before sleep, because no trial tested a small dose closer than that.
| Last drink | mg | Hours before sleep | Asleep 10pm | Asleep 11pm | Asleep midnight |
|---|---|---|---|---|---|
| Espresso, 1 shot | 63 | 4 | 6:00pm | 7:00pm | 8:00pm |
| Black tea, 8 oz | 47 | 4 | 6:00pm | 7:00pm | 8:00pm |
| Red Bull, 8.4 oz can | 80 | 5.8 | 4:15pm | 5:15pm | 6:15pm |
| Brewed coffee, 8 oz | 95 | 7 | 3:00pm | 4:00pm | 5:00pm |
| Monster, 16 oz can | 160 | 10.8 | 11:15am | 12:15pm | 1:15pm |
| Brewed coffee, 16 oz | 190 | 12 | 10:00am | 11:00am | noon |
| CELSIUS, 12 oz can | 200 | 12.4 | 9:40am | 10:40am | 11:40am |
| Pre-workout, 1 scoop | 254 | 14.1 | 7:55am | 8:55am | 9:55am |
The cup beats the clock
How the clock works
Almost all of a drink is absorbed within 45 minutes, so each one ramps in over 45 minutes. Then it halves: about every 5 hours on average, anywhere from 1.5 to 9.5 hours in healthy adults. The clock adds up every drink and shows the band for a half-life of 3 to 6 hours, the range a 2025 trial calls typical, so no answer is a single prescription.
The latest time works backward from your sleep: the hours it takes your last drink to fall to 40 mg, after what your earlier drinks still leave. Set a different half-life on your half-life page and the clock uses it.
Our two lines
These lines are ours, worked from the trials. Under 40 mg is low: the 2023 review's cutoffs, 8.8 hours for a 107 mg coffee and 13.2 hours for a 217.5 mg pre-workout, both leave 35 to 39 mg at bedtime on this model. 40 to 80 mg is in between: 100 mg 4 hours before bed leaves about 64 mg and showed nothing measurable in one trial. Over 80 mg is a measured cost: 400 mg 12 hours before bed leaves about 84 mg and still cut about 21 minutes of deep sleep.
Where the clock stops
It doesn't know how sensitive you are, the real size of your cup, or your real half-life. Coffee-shop cups vary a lot: one drink from the same shop measured 259 to 564 mg on six days. Very heavy days slow clearance further, so the halving fits ordinary amounts best. Check it against your own nights for two weeks.
11 sources
- Antonio J and others, Common questions and misconceptions about caffeine supplementation: what does the scientific evidence really show? Journal of the International Society of Sports Nutrition, 2024doi.org
- Gardiner C and others, Dose and timing effects of caffeine on subsequent sleep: a randomized clinical crossover trial, Sleep, 2025doi.org
- Gardiner C and others, The effect of caffeine on subsequent sleep: a systematic review and meta-analysis, Sleep Medicine Reviews, 2023doi.org
- Drake C, Roehrs T, Shambroom J, Roth T, Caffeine effects on sleep taken 0, 3, or 6 hours before going to bed, Journal of Clinical Sleep Medicine, 2013pmc.ncbi.nlm.nih.gov
- USDA FoodData Central, SR Legacy: brewed coffee (171890), espresso (171891), brewed black tea (173227) and brewed green tea (171917)fdc.nal.usda.gov
- Red Bull, How much caffeine is in a can of Red Bull?redbull.com
- The Coca-Cola Company, What is caffeine?coca-colacompany.com
- Monster Energy original, 16 fl oz, retail label listing (caffeine from all sources 160 mg)shaws.com
- CELSIUS Sparkling Kiwi Guava, 12 fl oz, retail label listing (caffeine 200 mg)shop.lowesfoods.com
- Jagim AR, Harty PS, Camic CL, Common Ingredient Profiles of Multi-Ingredient Pre-Workout Supplements, Nutrients, 2019doi.org
- Denaro CP and others, Clinical Pharmacology and Therapeutics, 1990 (clearance falls with repeated high daily doses)pubmed.ncbi.nlm.nih.gov
