Caffeine cut-off calculator
When to have your last coffee, tea, energy drink or pre-workout so it is not the reason you are awake at 1am - and whether today has gone over the 400 mg guide.
Why the 3pm coffee is wrecking your sleep
Caffeine has a half-life of around five hours in most adults - some people clear it in three, some in nine. A coffee at 3pm leaves roughly a quarter of its caffeine in your system at 1am. That is enough to fragment deep sleep even if you fall asleep fine, and deep sleep is where the recovery from training happens. The cut-off calculator works back from when you want to be asleep and tells you the last sensible time for a coffee, tea, energy drink or pre-workout.
How much is too much
The UK Food Standards Agency and the European Food Safety Authority both use 400 mg a day as the guide for healthy adults, and 200 mg for pregnant women. That is about four filter coffees, or two large energy drinks, or two pre-workout scoops - and pre-workout scoops are where people quietly blow past it, because 200 mg on top of the morning coffees is a lot. The figures per drink here are typical values; strength varies a lot between brands and pours, so read the can and treat coffee-shop figures as a rough guide.
Shift work and caffeine
On nights, caffeine at the start of the shift is useful. Caffeine in the last third of the shift is what stops you sleeping when you get home. Treat the time you plan to sleep as bedtime and count back the same six to eight hours - on a shift finishing at 6am with sleep at 7am, that means nothing after midnight to 1am. Our sleep calculator works out the sleep side.
FAQs
How long does caffeine stay in your system?
The half-life is about 5 hours in most adults, so half the caffeine is still there 5 hours later and a quarter after 10 hours. It ranges from about 3 to 9 hours depending on genetics, smoking, pregnancy and some medications.
What time should I stop drinking coffee?
For most people, 8 hours before bed - about 2pm for a 10pm bedtime. If you are sensitive, 10 hours. Even if you can fall asleep after a late coffee, the caffeine reduces deep sleep.
How much caffeine is safe per day?
The UK Food Standards Agency and EFSA guide is up to 400 mg a day for healthy adults and 200 mg during pregnancy. Above that, sleep disruption, anxiety and a racing heart become more likely; it is a guide for everyday intake, not a safety cliff.
How much caffeine is in pre-workout?
Typically 150 to 300 mg per scoop - check the label. Taken in the evening it will cost you sleep; taken on top of three coffees it puts most people over 400 mg for the day.
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