Sleep Calculator
Sleep runs in cycles of roughly 90 minutes, and waking at the end of one
beats waking in the middle. Pick your wake-up time and get bedtimes that
line up.
Runs entirely in your browser. Nothing you enter is sent anywhere.
Assumptions
7–9 hours (5–6 cycles) is the sweet spot for most adults, so those rows are highlighted. Cycle length is an average and varies from person to person; treat these as starting points, not medical advice.
Knowing your bedtime is the easy part. The hard part is that "one more video" at 11pm has a way of becoming 1am, and no calculator fixes that. The scroll doesn't feel like a decision while it's happening.
Hawser handles the same problem during the workday: it notices when you've drifted from what you meant to do on your PC and pulls you back before the time disappears. If your evenings vanish at a screen too, the day version is where it starts.
See how Hawser worksHow this is calculated
Working back from your wake time, we subtract whole sleep cycles (default 90 minutes) plus the time you take to fall asleep (default 15 minutes) to produce each bedtime. "Going to bed now" works forward the same way to suggest wake-up times. 3 to 6 cycles are shown; 5 and 6 (7.5 to 9 hours) are highlighted because that range suits most adults. Everything runs locally in your browser.