How much caffeine is in your system?
Caffeine in your system
Projected: one filter coffee at 18:22. Add what you've actually had to replace it.
Cycle-aligned wake-up times
Counting forward from your bedtime in 90-minute cycles. Waking at the end of a cycle tends to feel easier than waking mid-cycle. These are windows, not appointments — real cycles run 70 to 120 minutes and vary night to night.
- 04:55–05:35 4 cycles · 6 h of sleep
- 06:20–07:10 5 cycles · 7 h 30 min of sleep
- 07:45–08:45 6 cycles · 9 h of sleep
Add today's drinks and see how much is still with you now and at bedtime.
Four coffees before noon and four before eight are the same total and different nights.
How much caffeine is in what you drink
The honest answer is a range, not a number. A filter coffee is usually quoted at 95 mg, but the same 240 ml cup runs from about 70 to 140 mg depending on bean, roast, grind and how long the water sits with it. Espresso is more concentrated but smaller: a single is around 63 mg.
Cold brew is the one that surprises people — around 150 mg for the same volume as a filter coffee, sometimes 200. Energy drinks are more predictable because they are formulated rather than brewed: 80 mg for a small can, 160 mg for a large one. Pre-workout supplements are the widest range of all, from 150 to 350 mg a scoop.
This calculator uses the central value of each range. Treat the result as an estimate of a cup, not a measurement of yours.
| Drink | Serving | Caffeine | Range | Source |
|---|---|---|---|---|
| Espresso 212 mg/100 g × 0.30 = 63.6 mg | 30 ml | 63 mg | 47–75 | USDA record |
| Double espresso 212 mg/100 g × 0.60 = 127.2 mg | 60 ml | 126 mg | 94–150 | USDA record |
| Filter coffee 40 mg/100 g × 2.4 = 96 mg | 240 ml | 95 mg | 70–140 | USDA record |
| Instant coffee 26 mg/100 g × 2.4 = 62.4 mg | 240 ml | 62 mg | 30–90 | USDA record |
| Cold brew | 240 ml | 150 mg | 100–200 | Estimate |
| Latte espresso 63.6 mg per shot; milk contributes none | 1–2 shots | 77 mg | 63–126 | USDA record |
| Decaf 1 mg/100 g × 2.4 = 2.4 mg | 240 ml | 3 mg | 2–7 | USDA record |
| Black tea 20 mg/100 g × 2.4 = 48 mg | 240 ml | 47 mg | 25–60 | USDA record |
| Green tea 12 mg/100 g × 2.4 = 28.8 mg | 240 ml | 28 mg | 20–45 | USDA record |
| Matcha | 2 g | 70 mg | 40–90 | Estimate |
| Energy drink, small ROCKSTAR sugar free, 79 mg per 8 fl oz → 83 mg per 250 ml | 250 ml | 80 mg | 75–85 | USDA record |
| Energy drink, large NOS energy drink, 163 mg per 16 fl oz → 172 mg per 500 ml | 500 ml | 160 mg | 140–180 | USDA record |
| Cola 9 mg/100 g × 3.3 = 29.7 mg | 330 ml | 30 mg | 25–40 | USDA record |
| Dark chocolate 60–69% cacao, 24 mg per oz → 42 mg per 50 g; lower cacao less | 50 g | 40 mg | 25–60 | USDA record |
| Pre-workout | 1 scoop | 200 mg | 150–350 | Label |
| Caffeine tablet | 1 tablet | 100 mg | 50–200 | Label |
Where these numbers come from
Most of the figures in the calculator are read off the USDA National Nutrient Database, which publishes caffeine content per 100 grams. A 240 ml filter coffee is 40 mg per 100 g times 2.4, which is 96 mg. An espresso is 212 mg per 100 g over 30 ml, which is 64 mg. Instant coffee, black tea, green tea, decaf and cola are all derived the same way, and each one links to the exact database record.
Four are not: cold brew, matcha, pre-workout powder and caffeine tablets. There is no authoritative entry for any of them — cold brew depends entirely on the brew ratio, matcha on cultivar and grade, and the two supplements on whatever the label says. Those four carry working estimates with deliberately wide ranges, and the ranges are the honest part of the answer.
Daily limits
Health authorities generally put 400 mg a day as the level most healthy adults tolerate without ill effect — about four filter coffees. Pregnancy guidance is lower, usually 200 mg.
A daily total says nothing about sleep, though. Four coffees finished by noon and four spread until 8pm are the same number and completely different nights. What matters for sleep is what is still on board at bedtime, which is what the chart above shows.
Tolerance, and what it does not cover
Regular caffeine use blunts the subjective hit — the alertness and the jitters fade with habit. This is real, and it is why long-term drinkers can have an espresso after dinner without feeling wired.
It does not follow that sleep is unaffected. Tolerance to the sleep-disrupting effects appears to be weaker than tolerance to the felt effects, so "it does not keep me awake" and "it is not costing me sleep" are different claims. The Drake study found measurable sleep loss in people who did not report noticing it.
A worked example
A filter coffee at 08:00 and another at 13:30 is 190 mg of intake across the day — well inside a 400 mg limit.
By 23:00 the morning cup has decayed to 11.9 mg and the afternoon one to 25.5 mg, so 37.3 mg is still on board at bedtime.
That is a trace most people would not notice. Move the second coffee to 17:30 and it leaves 44.3 mg instead of 25.5 — the daily total is unchanged, and the amount at bedtime nearly doubles.
Common questions
How much caffeine is in a cup of coffee?
A 240 ml filter coffee averages about 95 mg, with a realistic range of 70 to 140 mg. A single espresso is around 63 mg, a double around 126 mg, and cold brew around 150 mg for the same volume as filter.
How much caffeine is too much in a day?
Up to 400 mg a day is generally considered acceptable for healthy adults — roughly four filter coffees. Guidance during pregnancy is typically 200 mg.
How much caffeine is in an energy drink?
Around 80 mg in a 250 ml can and 160 mg in a 500 ml can. They vary less than coffee because they are formulated to a specification rather than brewed.
Does caffeine build up over several days?
Slightly. With a 5-hour half-life, about 96% of a morning dose is gone by the next morning, so day-to-day carryover is small at normal intakes and matters more with very high doses or a much longer half-life.
Is caffeine in chocolate worth counting?
Usually only at the margins. 50 g of dark chocolate carries around 40 mg — comparable to a black tea — while milk chocolate carries far less.
What this cannot tell you
- Your own half-life. The 3-to-7-hour range for healthy adults is wide, and where you fall in it is genuinely unknown without testing. Every number here inherits that uncertainty.
- Your own sleep cycles. Ninety minutes is a population average; real cycles run 70 to 120 minutes and vary night to night, which is why bedtimes are shown as windows.
- The caffeine in the cup in front of you. Brew strength and cup size move filter coffee from 70 to 140 mg. The presets are central values from a range, not measurements.
- The effect of medication or liver impairment. Some drugs change caffeine clearance far more than anything modelled here. This tool does not attempt them.
- Anything about safety. It estimates sleep impact, and nothing it says bears on driving, operating machinery, or a cardiac question.
An educational estimate, not medical advice. Talk to a clinician about sleep or cardiac concerns.
Put this on your own site
The calculator embeds as a single iframe. It carries no ads, no analytics and no cookies inside the frame — it will not add anything to your page that you have not chosen — and it works on a phone at any width.
<iframe src="https://caffeinecurfew.com/embed" width="100%" height="1650" style="border:1px solid #e1e0d9;border-radius:12px" loading="lazy" title="Caffeine cutoff calculator"></iframe>
<p><a href="https://caffeinecurfew.com/">Caffeine Curfew</a></p> Set a starting point with the same options the page uses — for example a cold brew drinker with an eleven o'clock bedtime: /embed?bed=23:00&usual=cold-brew
The frame is tall enough for the chart at the narrowest width a phone will give it, so a wide column gets some slack at the bottom. The credit line under the frame is the only thing we ask for; please keep it.
References
Written by Toni Ristola — Built the calculator and wrote the explainers. Not a clinician.
Last updated 2026-08-30