Caffeine Half-Life Calculator: How Much Caffeine Is Left in Your Body?
Pick your drink, when you had it and a time to check (like bedtime) to see how much caffeine is still in your system.
- Nothing you type is stored
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Caffeine left at that time
38Caffeine per drink
- Caffeine taken
- 100 Caffeine per drink
- Still in your body
- 38%
- Below 50 mg by
- 9:00 PM
An estimate for general information, not medical advice.
Advised limits: 400 mg a day for adults, 200 mg in pregnancy.
Hour by hour
| Time | Hours after | Caffeine left (mg) |
|---|---|---|
| 4:00 PM | 0 | 100 |
| 5:00 PM | 1 | 87 |
| 6:00 PM | 2 | 76 |
| 7:00 PM | 3 | 66 |
| 8:00 PM | 4 | 57 |
| 9:00 PM | 5 | 50 |
| 10:00 PM | 6 | 44 |
| 12:00 AM | 8 | 33 |
| 2:00 AM | 10 | 25 |
| 4:00 AM | 12 | 19 |
| 8:00 AM | 16 | 11 |
| 12:00 PM | 20 | 6 |
| 4:00 PM | 24 | 4 |
How to use
- Choose your drink (or enter the caffeine in mg) and how many.
- Enter when you had it and the time you want to check.
- Read the caffeine left and the hour-by-hour table.
Good to know
Caffeine left = dose × 0.5^(hours ÷ half-life). The average half-life in healthy adults is about 5 hours, but it ranges from about 1.5 to 9.5 hours. It is longer in pregnancy and with some medicines and oral contraceptives, and shorter in smokers. Change it under More options.
Typical amounts (check labels, they vary): filter or brewed coffee about 100 mg a cup, instant coffee about 60 mg a teaspoon, espresso about 63 mg, a cup of chai about 40 mg, a 330 ml cola about 35 mg. Indian energy drinks are capped by FSSAI at 300 mg per litre, so about 75 mg in a 250 ml can.
Healthy adults are advised to keep below 400 mg a day, and pregnant women below 200 mg (EFSA). For better sleep many experts suggest no caffeine within about 6–8 hours of bedtime. Children and people with heart rhythm problems or anxiety should take much less.
Questions
How long does caffeine stay in your body?
About half is gone after 5 hours on average, a quarter remains after 10 hours, and it takes roughly a day to clear almost completely.
Will an evening coffee affect my sleep?
Often yes. A 4 PM coffee of 100 mg leaves about 38 mg at 11 PM with a 5-hour half-life, enough to disturb sleep in sensitive people.
How much caffeine is in a cup of chai?
Usually about 30–50 mg, depending on the tea, how long it is boiled and the cup size.
How much caffeine is safe in pregnancy?
Up to 200 mg a day is the usual advice. Ask your doctor, as the half-life is longer in pregnancy.
Is my data saved?
No. Everything is calculated on your device.