We built CycleRest because sleep questions deserve real answers.
Free tools built on published research. No accounts, no upsells, no vague wellness advice — just the science, applied directly to the questions you're actually asking.
Where this started
The questions that motivated CycleRest are simple ones. What time should I actually wake up? How much sleep have I lost this week? Is that afternoon coffee still affecting me right now? These aren't obscure research questions — they're things people search for every day. And they have real, calculable answers grounded in decades of sleep science.
We built tools that do that calculation properly — accounting for sleep onset latency, 90-minute cycle architecture, caffeine half-life variation by metabolism type, and cumulative sleep debt — and explain the reasoning behind every number we show you.
We're not a wellness brand. There's nothing to buy here and no account to create. Just tools that work, free for anyone who needs them.
How our tools actually work
Every calculator on CycleRest is built around specific published research, not general wellness guidelines. Here's what drives each one:
Sleep Cycle Calculator
Human sleep architecture moves through 90-minute cycles — light sleep, deep sleep (N3), and REM — repeated four to six times a night. Waking mid-cycle, particularly during N3, causes the grogginess most people attribute to other causes. Our calculator factors in the average 14-minute sleep onset latency, which is more precise than the round 15-minute figure most tools use, so the times we suggest align with natural cycle endpoints rather than arbitrary alarms.
Sleep Debt Tracker
Sleep debt is cumulative. Research shows cognitive performance degrades measurably with each night of insufficient sleep, and those deficits don't fully resolve after a single good night. Our tracker uses a rolling weekly calculation against age-adjusted targets — giving you an honest picture of your actual deficit, not just last night's hours.
Caffeine Half-Life Calculator
Caffeine's half-life varies significantly by person — from around 3.5 hours for fast metabolizers to 10 or more hours during pregnancy. The variation is driven primarily by the CYP1A2 liver enzyme. Our calculator lets you select your metabolism type and tracks stacked doses from multiple drinks, giving you a real-time picture of what's active in your system rather than a generic cutoff time.
What we believe about sleep
Sleep isn't a lifestyle variable you tweak on the margins. It's the period during which your brain consolidates memory, your body repairs tissue, and your glymphatic system clears the metabolic waste that accumulates while you're awake — including proteins associated with neurodegenerative disease. There's no supplement, morning routine, or productivity system that compensates for consistently cutting it short.
Most people who struggle with sleep aren't doing so because of poor discipline. They're working against schedules, environments, and information gaps that aren't set up for good sleep. Accurate information closes some of that gap. That's the role we're trying to play.
CycleRest is an educational resource, not a medical provider. If you're dealing with chronic insomnia, suspected sleep apnea, or any condition genuinely disrupting your health, please speak with a doctor or sleep specialist. Our tools are designed for healthy adults looking to understand and improve their sleep patterns — they're not a substitute for clinical evaluation.
Your data stays with you
Every calculation on CycleRest runs entirely in your browser. We don't log your sleep times, your caffeine intake, or anything else you enter. We don't sell data or build user profiles. Sleep is personal — we treat it that way.
Questions or feedback
If something in our tools is inaccurate, or if there's a sleep-related question you haven't been able to find a clear answer to, we'd genuinely like to know.
© 2026 CycleRest. Built for the global community.