About SleepCycle
SleepCycle exists because the worst part of a short night is waking deep in the wrong phase.
Sleep runs in ~90-minute cycles, and waking from deep sleep produces sleep inertia — up to 30 minutes of grogginess that no amount of coffee fully fixes. Cycle-aware bedtimes and wake times cannot add hours to your night, but they can change which phase your morning alarm lands in. That is a real, mechanical improvement.
The same is true of caffeine: it is not about willpower, it is about half-life arithmetic. And naps: the difference between a 20-minute refresh and an 80-minute hangover is which cycle phase you interrupt.
We are educators, not clinicians, and we sell no mattresses, supplements, or subscriptions. The calculators exist to make sleep scheduling something you can check, not guess.
What makes SleepCycle different
- Your numbers never leave your browser. Every calculator on SleepCycle runs entirely on your device. We never see, store, or transmit the figures you enter — there are no accounts and no server-side processing of your inputs.
- Published methodology. Each calculator page explains the exact formula it uses and the assumptions behind it, so you can check our work or reproduce it in a spreadsheet.
- Free, forever, without a paywall. SleepCycle is supported by advertising. There is no premium tier, no email gate, and no upsell.
Independence
SleepCycle is an independent educational project. We are not affiliated with, endorsed by, or acting on behalf of any government agency, lender, insurer, or the organizations whose formulas and public data we reference (such as published sleep-medicine research (AASM, NSF guidance)). All trademarks and referenced standards belong to their respective owners.
Questions, corrections, or suggestions are genuinely welcome — get in touch.