Caffeine Calculator
Add what you drank today — see how much caffeine is still active and how much will be left at bedtime.
Caffeine content of common drinks
| Drink | Caffeine (mg) | Left after 8 h* |
|---|---|---|
| Brewed coffee (240 ml) | 95 | 31 |
| Espresso shot | 63 | 21 |
| Double espresso | 126 | 42 |
| Cold brew (470 ml) | 200 | 66 |
| Latte / cappuccino | 75 | 25 |
| Instant coffee | 62 | 20 |
| Black tea | 47 | 16 |
| Green tea | 28 | 9 |
| Matcha (1 tsp) | 70 | 23 |
| Cola (330 ml) | 34 | 11 |
| Energy drink (250 ml) | 80 | 26 |
| Energy drink (500 ml) | 160 | 53 |
| Pre-workout scoop | 200 | 66 |
| Dark chocolate (50 g) | 40 | 13 |
*With an average 5-hour half-life. Values are typical; brands and brew strength vary widely.
How it works
Each drink is absorbed over roughly 45 minutes and then eliminated exponentially with the half-life you choose (a one-compartment model). The 50 mg line is a practical sleep-friendly threshold, not a medical cut-off. This is an estimate for information only. All calculations happen in your browser.
How long does caffeine stay in your system?
Caffeine has an average half-life of about 5 hours in healthy adults, with a normal range of roughly 3 to 7 hours. After two half-lives a quarter of the dose is still active, so a 3 pm coffee can still be working at 11 pm.
When should I stop drinking coffee before bed?
A common guideline is at least 8 hours before bedtime. In a sleep-lab study, 400 mg taken even 6 hours before bed cut total sleep by about an hour. Use the calculator to find when your own total drops below a sleep-friendly level.
How much caffeine per day is safe?
For healthy adults, up to 400 mg a day is generally considered safe (FDA, EFSA), with no more than about 200 mg at once. During pregnancy the usual advice is to stay under 200 mg a day. Sensitivity varies a lot between people.
What affects caffeine half-life?
Smoking speeds it up (around 3 hours). Pregnancy, oral contraceptives, liver conditions and some medications slow it down, sometimes to 10 hours or more. Genetics (the CYP1A2 enzyme) also make some people fast or slow metabolisers.