Caffeine Half-life Calculator

Add today’s coffee, milk tea or cola and see how much caffeine is still working in your body at bedtime.

Track caffeine remaining in your body

Time

Drink

Caffeine (mg)

Metabolism

Planned bedtime tonight

* Preset amounts are typical references — check product labels. Half-life varies significantly between individuals.

Caffeine

What does half-life mean?

Caffeine’s plasma half-life is roughly 4–6 hours (with large individual variation): each half-life, the amount in your body halves. A 95 mg coffee at 4 pm still has about half working at 9 pm, and possibly 30–50 mg left at bedtime.

How much is safe?

Healthy adults are generally advised to stay under 400 mg per day; getting below ~50 mg by bedtime has little effect on falling asleep for most people. Be more conservative if you are caffeine-sensitive, pregnant, or have cardiovascular conditions.

Related: Diet and sleep

FAQ

Do milk tea and tea contain caffeine too?

Yes. A cup of milk tea often carries 30–100 mg (depending on the tea base and size), green/black tea about 25–50 mg, cola about 34 mg per can. Many “can’t sleep” nights trace back to an overlooked afternoon milk tea.

I can fall asleep after evening coffee — so no harm?

Falling asleep is not sleeping well. Even when caffeine doesn’t block sleep onset, it reduces deep sleep and increases night awakenings — and next-day drowsiness invites more coffee, closing the loop.

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Tool results are for reference only and do not constitute medical advice.

Track caffeine remaining in your body

What does half-life mean?

How much is safe?

FAQ

How much does caffeine affect your sleep?