Coffee you love.
Sleep you need.
Most advice treats them as enemies. We think they've just been badly introduced. JavaSleep is a slow magazine about the hours between your last sip and your first dream — with honest reviews, quiet science, and one very useful calculator.
How much caffeine
will still be awake
at your bedtime?
Caffeine doesn't clock out when you do. It has a half-life of about five hours, which means your 3 PM latte is still at half strength when you're trying to fall asleep at 11. Here's the honest math.
Adjust the inputs above to see your personal timeline.
Three things worth reading slowly.
Best Travel CPAP Machines (2026): AirMini vs. Transcend Micro vs. Z2 Auto
The best travel CPAP machine for most people is still the ResMed AirMini — if you can tolerate its waterless humidification and proprietary tubing.
Sleep Inertia and Morning Grogginess: What Light Can Fix, and What It Can't
Nine volunteers at a Harvard-affiliated sleep lab did simple arithmetic at intervals after waking. In the first few minutes, their performance was worse than it was after more than a day without…
Do Health Metrics Change Anything? A Six-Week Smartwatch Review
The question I kept asking before I bought one is probably the one you're asking now: will a $349 watch change anything I actually do, or will it just show me, in nicer graphics, that I sleep badly…
“The most civilized thing a person can do is enjoy a cup of coffee at ten in the morning and still sleep at ten at night.— Editor's Note, Issue №001