Sleep Window

Find your best bedtime and wake-up windows with a 90-minute sleep cycle calculator. Free planning tool by Hypnothera.

Sleep Window is a free sleep cycle calculator and bedtime calculator for Chrome. Plan when to sleep and when to wake using classic 90-minute sleep cycles — locally, privately, with no account. What you get • Wake mode — Enter when you need to wake up. See suggested bedtimes for 3, 4, 5, and 6 cycles. • Sleep mode — Enter when you’re going to bed, or tap Sleep now, to see best wake-up times. • 5-cycle highlight — 7.5 hours is called out as a balanced default window. • Fall-asleep buffer — Adjust 0–30 minutes (default 14) so the math matches how long you usually take to drift off. • Optional bedtime reminder — Opt in to a local Chrome notification before your planned wind-down. Nothing is sent to a server. • 2-minute wind-down — A short guided breathing exercise in the popup (offline visual pacer). This is a planning heuristic, not medical advice, not a medical device, and not a treatment for insomnia or any condition. Made by Hypnothera. Explore free tools and sleep hypnosis sessions at hypnothera.ai.