Example: I need to wake up at — hour (24h): 6 h · Minutes: 30 min → Best bedtimes: 9:15 PM or 10:45 PM.
For 9 hours (6 cycles): 9:15 PM
For 7.5 hours (5 cycles): 10:45 PM
For 6 hours (4 cycles): 12:15 AM
Frequently asked questions
How do I calculate sleep? Enter your numbers above and the result updates instantly. For example: I need to wake up at — hour (24h): 6 h · Minutes: 30 min → Best bedtimes: 9:15 PM or 10:45 PM.
Is this Sleep Calculator free? Yes — completely free with no sign-up or paywall. It runs entirely in your browser and keeps working offline; the numbers you enter never leave your device.
How accurate is it? It uses the standard published formula for sleep. Results are estimates for planning — not financial, tax, medical, engineering, or legal advice.