Complete guide
Sleep
Sleep is the foundation nearly everything else stands on — mood, focus, and how anxious you feel all ride on it. Yet it’s the first thing most people sacrifice under pressure, and the loss compounds quietly.
This guide brings together the sleep science behind our tools: how cycles work, what sleep debt really is, why afternoon coffee costs you at midnight, and what actually helps you drop off.
Sleep runs in cycles
Sleep isn’t uniform — it moves through roughly 90-minute cycles of lighter and deeper stages. Waking at the end of a cycle, rather than mid-deep-sleep, tends to feel far easier. Timing your bedtime to land your alarm at a cycle boundary is a small change with an outsized payoff.
Sleep debt is real and it compounds
Every hour short of what you need adds to a running total. You can repay some of it, but not all in one lie-in — recovery comes from a sustained return to adequate nights. Big debts degrade mood, judgment, and health, and they show up in anxiety, too.
Caffeine outstays its welcome
Caffeine has a half-life of about five hours for a typical adult — longer if you metabolize slowly. That 3pm coffee can leave a meaningful dose still circulating at bedtime, lightening and fragmenting your sleep even if you fall asleep fine. The fix is usually timing, not quantity.
What helps you drop off
A wind-down routine, a dark cool room, a long slow exhale, and steady background sound all help. Our generated sounds — white, brown, pink, ocean, rain — are made live in your browser, so there’s no loop to notice and they keep playing offline.
Related tools
Sleep Cycle Calculator
Sleep cycle calculator: enter your wake-up time and get the best bedtimes based on 90-minute sleep cycles plus time to fall asleep. Free and instant.
Sleep Debt Calculator
Add up your last week of sleep and see your sleep debt in hours, what it does to you, and a realistic recovery plan. Free, instant, private.
Caffeine Half-Life Calculator
Caffeine half-life calculator: enter your coffee and timing to see how many mg are still in your system at bedtime, with fast/slow metabolizer settings.
White Noise
Clean, generated white noise with a sleep timer and volume fade. No loops, no ads in the audio, works offline — free in your browser.
Brown Noise
Deep, low-frequency brown noise generated live in your browser — the warm rumble many people find steadier than white noise. Sleep timer included.
Rain Sounds
Soft, steady rain generated in your browser — endless, seamless, and free, with a sleep timer and volume fade for drifting off.
The Worry Timer
Give every worry an appointment: capture it, set when you'll deal with it, and run a contained worry session with a timer. A classic CBT technique, private in your browser.