The Caffeine Curfew
Move your last coffee and get your sleep back.
People who sleep badly usually blame the evening. The actual cause is often something they drank seven hours before they went to bed and forgot about entirely.
Caffeine takes around five hours to fall to half its level in an average person, but the real range runs from roughly ninety minutes to nine hours, and some people clear it far slower again. An afternoon coffee is often still meaningfully present at bedtime. It may not stop you falling asleep, but it can flatten the deep sleep you get, which is why you can sleep eight hours and still wake up tired.
Count back at least six hours from bedtime
A controlled trial found caffeine taken six hours before bed still measurably cut total sleep time. Six hours is the floor, not the target. If you suspect you clear it slowly, push it earlier.
Move it, do not cut it
Keep the same number of coffees. Just pull them earlier. Cutting caffeine entirely is a different and much harder project.
Expect three rough days
Shifting the timing gives most people a mild afternoon slump for a few days. It passes and it is worth sitting through.
Give it two weeks before judging
Sleep quality changes are gradual. One night tells you nothing.
Go deeper
What the paid version adds to this one.
How to find your own clearance window rather than using the average
What to replace the afternoon coffee with that is not just sugar
The interaction with alcohol, which compounds the same problem
A filmed two-week shift, including the slump days