Caffeine calculator
Choose what you drank and when. The curve below is the same pharmacokinetic model the CaffIQ app runs, at its free settings.
70 mg — a typical cup; published range 60–80 mg
What that does to your evening
Peaks at 1.25 mg/L around 17:26.
Back under the sleep-friendly level at 19:33
3 hr 33 after your cup.
The “sleep-friendly level” is 1.0 mg/L of caffeine in plasma, the point below which it is not expected to interfere with sleep. It is the app’s free-tier threshold.
Common cups, at a glance
Every drink at its midpoint dose, with the time it takes to fall back under the sleep-friendly level.
| Drink | Peak | Back under the level after |
|---|---|---|
| Espresso (single, 30 ml) | 1.25 mg/L | 3 hr 33 |
| Filter coffee (240 ml) | 2.14 mg/L | 7 hr 26 |
| Cold brew (240 ml) | 2.24 mg/L | 8 hr 09 |
| Instant coffee (240 ml) | 1.07 mg/L | 2 hr 21 |
| Decaf (240 ml) | 0.05 mg/L | — |
| Black tea (240 ml) | 0.80 mg/L | — |
| Green tea (240 ml) | 0.54 mg/L | — |
| Matcha (2 g) | 1.16 mg/L | 2 hr 59 |
| Energy drink (250–500 ml) | 2.07 mg/L | 7 hr 35 |
| Cola (355 ml) | 0.66 mg/L | — |
| Energy shot (60 ml) | 3.45 mg/L | 11 hr 16 |
What this assumes
- A 70 kg adult. Body weight dilutes the dose — it lowers the peak without changing how fast you clear it.
- A five-hour half-life, the average-adult reference. Real clearance ranges roughly two to ten hours between people, driven by genetics, hormones, smoking and medication.
- An empty stomach. Food slows absorption, so a coffee after a meal peaks later and flatter.
- The midpoint of each published range. Your actual cup can sit either side of it.
How a caffeine calculator works, and what makes one accurate
What this page had to simplify
Read that list again as two columns. Every assumption above is a real variable, frozen here because a web page cannot know you — and read from your own data by the app instead.
| This page | CaffIQ |
|---|---|
| One drink, on its own | Every drink of your day, stacked on what is still circulating |
| A 70 kg adult | Your own body weight |
| A flat five-hour half-life | Your own clearance — genetics, hormones, smoking, age |
| An empty stomach | When you actually ate |
| The midpoint of a published range | The cup you actually logged |
| One frozen calculation | Your level live, and the cutoff hour that follows from it |
One cup, one estimate. CaffIQ does this for every drink, all day, tuned to your body.
Download on the App StoreCaffIQ provides general estimates, not medical advice. For any health question, talk to a qualified professional.