Body & diet / Sleep
Caffeine Calculator: How Much Is Left at Bedtime?
Enter your coffee, tea, and energy drinks with the time of each to see how much caffeine is still in your body at bedtime, when it falls below 50 mg, your total for the day against the 400 mg limit, and a curve over 24 hours.
Caffeine Calculator: How Much Is Left at Bedtime?: Each drink decays by half every half-life, 5 hours by default, and the amounts left are added up. Coffee at 8:00 (95 mg), an espresso at 11:00 (63 mg), and coffee at 15:00 (95 mg) leave about 55 mg at 23:00, from a total of 253 mg, and fall below 50 mg at about 23:45. Runs 100% locally in your browser with zero server file uploads.
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Caffeine leaves the body at a steady rate: in healthy adults about half is gone in roughly 5 hours, though it ranges from about 2 to 10 hours and is longer during pregnancy and with some medicines. The drink amounts are typical, not exact: a 240 ml cup of brewed coffee has about 95 mg, an espresso shot about 63 mg, black tea about 47 mg, and green tea about 28 mg. Health authorities consider up to 400 mg a day safe for healthy adults, and 200 mg during pregnancy.
Sleep
Caffeine blocks adenosine, which builds sleep pressure during the day. A 2013 study found that 400 mg taken even six hours before bed cut total sleep by more than an hour, so many people keep to a cut-off in the early afternoon.
Bedtime
To time your sleep in whole sleep cycles, use the sleep calculator.
How to use it
- Enter each drink as a time and its milligrams of caffeine.
- Set your bedtime and, if you know it, your caffeine half-life.
- Read the caffeine at bedtime and the day's total.
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Related tools
Frequently asked questions
How much caffeine is too much?
Health authorities in the US and Europe consider up to 400 mg a day safe for most healthy adults, and up to 200 mg a day during pregnancy; single doses of up to 200 mg are not a concern.
Why does caffeine affect me differently?
The half-life ranges from about 2 to 10 hours between people: smoking shortens it, while pregnancy, oral contraceptives, and liver problems lengthen it.
How much caffeine is in my drink?
It varies with the beans, brewing, and brand. Typical values: brewed coffee 95 mg per 240 ml, espresso 63 mg per 30 ml shot, black tea 47 mg, green tea 28 mg; check the label of energy drinks and colas.
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