Caffeine Half-Life Calculator: How Much Caffeine Is Left at Bedtime?
How long does caffeine last? In healthy adults caffeine has an average half-life of about 4 hours, with a range of 2 to 8 hours1. So half of a 96 mg cup of coffee is still in your body 4 hours later, and a quarter after 8 hours. Add your drinks and bedtime below to see how much caffeine will be left when you go to sleep.
Your drinks today
Caffeine still in your body at bedtime
How the caffeine half-life calculator works
Choose each drink and the time you had it. The calculator uses average caffeine values per cup2 and assumes the amount in your body halves every few hours. You can pick a faster (3 hours), average (4 hours) or slower (6 hours) half-life, within the 2 to 8 hour range EFSA reports for healthy adults1. It then draws your caffeine curve, shows the peak, the time it drops below 100 mg and how much is left at bedtime.
Why 100 mg? EFSA notes that single doses of 100 mg may affect sleep duration and patterns in some adults, particularly close to bedtime13. The overall guideline for healthy adults is up to 400 mg a day, or 200 mg a day during pregnancy. To count your daily total, use our caffeine calculator.
Caffeine left at 11 pm from one cup of coffee
| Cup of brewed coffee (96 mg) at | Hours before 11 pm | Left with a 4-hour half-life | Left with a 6-hour half-life |
|---|---|---|---|
| 7 am | 16 | 6 mg | 15 mg |
| 10 am | 13 | 10 mg | 21 mg |
| 1 pm | 10 | 17 mg | 30 mg |
| 4 pm | 7 | 29 mg | 43 mg |
| 7 pm | 4 | 48 mg | 60 mg |
| 9 pm | 2 | 68 mg | 76 mg |
Tips for enjoying caffeine and sleeping well
- Set a cut-off time: pick a time for your last cup and check it here against your bedtime.
- Remember hidden caffeine: karak, matcha, cola and energy drinks all count. See does karak tea have caffeine.
- Switch to caffeine-free drinks in the evening: date latte, rooibos, hibiscus or a saffron herbal infusion.
- In Ramadan, caffeine is squeezed into the hours between iftar and suhoor, so timing matters even more. Read caffeine in Ramadan.
If you are pregnant, take medicines or often struggle to sleep, ask your doctor how much caffeine is right for you. See all our free drink calculators.
Caffeine half-life: frequently asked questions
What is the half-life of caffeine?
For healthy adults, the European Food Safety Authority gives an average half-life of about 4 hours, with a range of 2 to 8 hours. That means about half of the caffeine you drink is still in your body 4 hours later.
How long does caffeine stay in your system?
With a 4-hour half-life, a 96 mg cup of coffee drops to about 48 mg after 4 hours, 24 mg after 8 hours and 12 mg after 12 hours. After about 5 half-lives, roughly 20 hours, only around 3% is left.
When should I stop drinking coffee before bed?
It depends on how much you drink and how fast you clear caffeine. With an average 4-hour half-life, a cup of brewed coffee 8 hours before bed leaves about 24 mg at bedtime. Use the calculator with your own drinks and bedtime to find your cut-off.
How much caffeine at bedtime affects sleep?
EFSA notes that single doses of 100 mg may affect sleep duration and patterns in some adults, particularly when consumed close to bedtime. The calculator warns you when 100 mg or more is left at bedtime.
Which drinks have no caffeine?
Herbal and fruit drinks such as rooibos, hibiscus and date latte are caffeine-free, and decaf coffee has only about 2 mg a cup. They are good choices for the evening.
Sources
- European Food Safety Authority. EFSA explains: caffeine. efsa.europa.eu
- Mayo Clinic. Caffeine content for coffee, tea, soda and more. mayoclinic.org
- EUFIC. EFSA opinion on the safety of caffeine. eufic.org
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