Why afternoon coffee is the problem
Because caffeine stays in your body for 5–6 hours at half strength, a 4 pm cup can still be half-present around 9:30 pm. For a person who sleeps at 23:00, that is enough to delay sleep and lighten the sleep you get.
A simple cutoff rule
Work backwards from your bedtime:
- Bedtime 22:00 → last coffee around 12:00–14:00
- Bedtime 23:00 → last coffee around 13:00–15:00
- Bedtime 00:00 → last coffee around 14:00–16:00
If you are sensitive to caffeine, push the cutoff earlier. If you rarely feel effects, you may be fine a little later — but most people underestimate how much late caffeine affects them.
Small habits that help
- Switch to decaf or herbal tea after your cutoff.
- Keep the same cutoff on weekends.
- Watch hidden caffeine in cola, energy drinks, chocolate, and some painkillers.
Why the cutoff feels like a rule
People ask why a specific time matters when they feel fine in the evening. The reason is that caffeine is slow to leave. At 5-6 hours it is only half gone, so an afternoon cup is still meaningfully present at bedtime — not enough to feel, but enough to shorten deep sleep and delay the moment you drift off.
That is also why a cutoff feels more useful than a rule about total caffeine: the same 200 mg is harmless at 8 am and disruptive at 5 pm. Timing, not just the amount, decides how it affects your night.
Test your own cutoff for a week
The general numbers here are a starting point, not a verdict. Run a simple week-long test: choose a cutoff time, stick to it, and compare how you sleep against a week when you drank later. Most people discover their own pattern quickly, and the answer is usually earlier than they guessed.
For persistent sleep problems, talk to a doctor. This page is a general timing guide, not medical advice.