About SleepCycle Calc
SleepCycle Calc is a free sleep cycle calculator that helps you decide the best time to go to bed or wake up, so you rise feeling rested instead of groggy. No sign-up, no app to install — just open the page and plan your night.
Why we built it
Most people know they should sleep 7–9 hours, but few know that when you wake up matters as much as how long you sleep. Sleep runs in ~90-minute cycles. An alarm that cuts through deep sleep leaves you tired, while waking at the end of a cycle feels natural. We wanted a dead-simple tool that turns this science into a 10-second answer.
What you get
- Wake-up planning: enter the time you must get up, and we list the best bedtimes.
- Bedtime planning: enter when you'll sleep, and we list the ideal wake-up times.
- Cycle-based results: every suggestion is a full 90-minute cycle, with a 15-minute allowance for falling asleep.
- Privacy by design: your inputs never leave your browser.
Our approach
The calculator is based on well-established sleep research showing that adult sleep is organized into repeating cycles of approximately 90 minutes, each containing light sleep, deep (slow-wave) sleep, and REM sleep. Completing whole cycles and waking near a cycle boundary tends to feel less jarring. We highlight 6-cycle (~9h) and 5-cycle (~7.5h) options because they sit in the recommended 7–9 hour range for adults.
How we keep it free
SleepCycle Calc is free to use. We keep the lights on through affiliate links — when you buy a product we recommend, we may earn a small commission at no cost to you. This never changes what the calculator tells you. Read our Affiliate Disclosure and Privacy Policy for the details.