Calculator
How much caffeine is left when you go to bed?
Add what you drank today and when. The curve shows what your body clears, hour by hour, right up to bedtime.
Add a drink to get started
The 100 mg mark is the EFSA threshold above which falling asleep may take longer.
Your day
- 1 Set the time of the drink
- 2 Tap the drink you had then
- 3 Repeat for every drink of the day
Rather not type it all in? Load a typical day:
A drink that isn't listed? Enter its caffeine content, shown on the label or the maker's website.
In the app, custom drinks are saved and come back in one tap.
🔒 Everything is worked out in your browser. No data is sent or stored.
Drinks logged
How this calculation works
Caffeine does not vanish all at once: it is absorbed over about an hour, peaks, then declines steadily. This calculator reproduces both phases with a one-compartment model, the standard way pharmacokinetics describes a swallowed substance.
C(t) = D × ka / (ka − ke) × ( e−ke·t − e−ka·t )
- 5 hElimination half-life in a healthy adult
- ≈ 45 minTime to peak, a consequence of absorption
- 100 mgSleep alert threshold (EFSA)
- 400 mgDaily amount of no concern (EFSA)
What the curve shows — and what it doesn't
The line represents the estimated amount of caffeine present in your body, in milligrams. Not a blood concentration, and not a measure of how strongly you feel it. The peak around 45 minutes marks the moment absorption stops outpacing elimination — the effects themselves start well before that, from 15 to 30 minutes in.
The green band marks the zone below 100 mg. EFSA uses this figure as the amount above which caffeine, taken close to bedtime, may lengthen the time it takes to fall asleep and shorten sleep. It is not a hard line: sensitivity varies widely between people.
Why the half-life isn't adjustable here
You will find calculators that let you set your own half-life. We deliberately don't. It depends on factors no form can measure: your CYP1A2 genetic variant, smoking, oral contraception, pregnancy, certain medications. Smoking roughly halves it; oral contraception can double it. Offering a slider would amount to asking you to pick a number at random, then dressing it up as precision.
So we use the population average, 5 hours, while accepting that your own figure may differ considerably. The only honest personalisation comes from observation: comparing your evening caffeine against your actual sleep over several weeks. That is what PauseCafé's insights do, using data from the Health app.
The amounts shown are averages
An espresso can range from 60 to 120 mg depending on the grind, the variety and the extraction time. The values offered here are typical orders of magnitude. For accurate tracking, PauseCafé records the real content of every drink, including your own custom ones.
Caffeine content of common drinks
The values used by the calculator, and how much they really vary. The same coffee can differ twofold depending on the grind, the variety and the extraction time.
| Drink | Small (S) | Medium (M) | Large (L) |
|---|---|---|---|
| Coffee | |||
| ☕ Espresso | 77 mg 30 ml | 154 mg 60 ml | 231 mg 90 ml |
| ☕ Lungo | 69 mg 80 ml | 95 mg 110 ml | 130 mg 150 ml |
| ☕ Filter coffee | 68 mg 150 ml | 108 mg 240 ml | 158 mg 350 ml |
| 🥛 Cappuccino | 77 mg 150 ml | 77 mg 250 ml | 154 mg 350 ml |
| ☕ Decaf coffee | 3 mg 150 ml | 5 mg 240 ml | 7 mg 350 ml |
| Tea | |||
| 🍵 Black tea | 42 mg 200 ml | 50 mg 240 ml | 73 mg 350 ml |
| 🍵 Green tea | 25 mg 200 ml | 30 mg 240 ml | 44 mg 350 ml |
| 🍵 Decaf tea | 4 mg 200 ml | 5 mg 240 ml | 7 mg 350 ml |
| 🌿 Herbal tea | 0 mg 200 ml | 0 mg 240 ml | 0 mg 350 ml |
| Soft drinks | |||
| 🥤 Cola | 30 mg 250 ml | 40 mg 330 ml | 61 mg 500 ml |
| 🥤 Diet cola | 35 mg 250 ml | 46 mg 330 ml | 70 mg 500 ml |
| Energy drinks | |||
| ⚡ Energy drink | 80 mg 250 ml | — | 160 mg 500 ml |
Frequently asked questions
How much caffeine is left in my body at bedtime?
It depends on how much you drank, when, and on your metabolism. With an average half-life of 5 hours, an 80 mg espresso taken at 3pm leaves about 27 mg by 11pm; the same coffee at 6pm leaves 41 mg. This calculator adds up what remains from each of your drinks at your exact bedtime.
What is the half-life of caffeine?
It is the time your body takes to clear half the caffeine present. In a healthy adult it averages 5 hours, with a documented range of 1.5 to 9.5 hours according to the Institute of Medicine. After 5 hours half the dose remains, after 10 hours a quarter, after 15 hours an eighth.
Why can't I adjust my half-life here?
Because no form can measure it. It depends on your CYP1A2 genetic variant, smoking, oral contraception, pregnancy or certain medications. Smoking roughly halves it; oral contraception can double it. Offering a slider would amount to asking you to pick a number at random, then dressing it up as precision. So we use the population average of 5 hours, accepting that your own figure may differ.
At what level does caffeine interfere with sleep?
EFSA uses 100 mg as the threshold above which caffeine taken close to bedtime may lengthen the time it takes to fall asleep and shorten sleep. It is not a hard line: sensitivity varies widely. Some people sleep after an evening espresso; others are affected by a 4pm tea.
How much caffeine per day is reasonable?
EFSA considers 400 mg per day to be of no concern for healthy adults, and 200 mg for a single dose. For pregnant or breastfeeding women the figure drops to 200 mg per day. These are population benchmarks, not individual limits.
Can you speed up caffeine elimination?
No, no reliable method speeds it up. Drinking water, walking or taking a shower may improve how you feel, but only time actually clears caffeine. The one effective strategy is to move your intake earlier in the day.
Does decaf coffee contain caffeine?
Yes, but very little: around 12 mg per decaf espresso, against 80 mg for a regular one. At that level the impact on sleep is negligible for the vast majority of people.
⚕️ Important. This calculator is for information and general wellbeing only. It is not medical advice, a diagnosis or a prescription. The effects of caffeine vary greatly from one person to another. If you have questions about your intake, trouble sleeping, or any concern about pregnancy, medical treatment or a health condition, speak to a healthcare professional.
Sources
- EFSA, Scientific Opinion on the safety of caffeine, 2015 — EFSA Journal 2015;13(5):4102. Thresholds of 400 mg per day, 200 mg per single dose, 100 mg for sleep impact.
- Institute of Medicine / National Academy of Sciences, Pharmacology of Caffeine — average half-life of about 5 h in a healthy adult, range 1.5 to 9.5 h.
- Pharmacokinetic literature — plasma peak reached between 30 minutes and 2 hours after intake.
Embed this calculator on your site
Running a blog, a roastery site or a wellbeing magazine? This calculator is free to embed. Copy the code below and paste it into your page: the tool stays up to date on its own, with nothing to install.
One condition only: keep the attribution link to PauseCafé shown under the tool.
How much caffeine is in each drink?
The detail drink by drink, with real ranges and the factors behind them.
This curve, all day long
PauseCafé keeps it updated on iPhone and Apple Watch, from the drinks you actually have.
