Snoozi is a free, no-login sleep calculator. You set a bedtime or a wake time, and it works back the other way in 90-minute sleep cycles, so you land on times that let you wake between cycles instead of mid-deep-sleep.
A sleep cycle runs roughly 90 minutes through light, deep and REM stages. Waking at the seam between cycles is the reason six hours can feel better than seven. Snoozi shows you those seams, plus a 15-minute fall-asleep buffer so you actually get the sleep you plan for.
Beyond timing, Snoozi helps you understand your own clock. The chronotype quiz places you as a Lion, Bear, Wolf or Dolphin — a framework popularised by Dr. Michael Breus that describes when your body naturally wants to sleep and rise. The circadian wheel then shows your wind-down window and caffeine cutoff against that rhythm.
Sleep debt is the part most people miss. Small nightly shortfalls add up fast, and they show up as mood, focus and appetite long before they show up as exhaustion. The sleep debt gauge tracks the gap between what you need and what you are actually getting, and estimates how long it takes to repay.
Everything here is free, works on your phone, and never asks you to sign in. If your debt is high, an optional one-time Sleep Reset Plan is available for purchase — that is the only paid part of Snoozi, and it is entirely optional.
Snoozi is an educational tool, not medical advice. If you consistently struggle with sleep, talk to a clinician. Snoozi is not affiliated with any other app or website using a similar name.