Add each drink with the time you had it. The calculator totals your caffeine for the day and uses caffeine’s half-life to estimate how much is still in your body when you go to bed.
Each drink uses a typical caffeine amount: about 95 mg in an 8 oz (240 mL) mug of brewed coffee, 63 mg in a single espresso shot, 47 mg in black tea, 28 mg in green tea, 34 mg in a 12 oz can of cola, and 80 mg in a small 250 mL energy drink. You can also enter your own amount in mg.
The US Food and Drug Administration says up to 400 mg a day is not generally associated with negative effects for healthy adults, and many health bodies advise no more than 200 mg a day during pregnancy. Caffeine sensitivity varies a lot from person to person.
Your body clears caffeine gradually, halving the amount roughly every 3–7 hours (about 5 on average). So a 200 mg coffee at 3 pm still leaves around 76 mg in your system at 10 pm, enough to affect sleep for many people. The calculator adds up what remains from every drink at your bedtime.
For healthy adults, the FDA and European Food Safety Authority consider up to about 400 mg a day (roughly four mugs of brewed coffee) generally safe. During pregnancy, the usual advice is under 200 mg a day.
Its half-life is typically about 5 hours, ranging from roughly 3 to 7 hours in healthy adults and longer in pregnancy or with some medications. After 5 hours about half remains; after 10 hours about a quarter.
Many sleep experts suggest no caffeine within 6–8 hours of bedtime. Use the calculator to see how much would still be active when you plan to sleep.
A single espresso shot has about 63 mg, while a 240 mL mug of drip coffee has about 95 mg. Espresso is stronger per millilitre but a typical serving is smaller.
Not completely. Decaf coffee usually has 2–15 mg per cup, which can add up if you drink a lot of it.
