Free, science-based tools to find your perfect bedtime, discover your chronotype, and understand your sleep debt — no sign-up required.
Enter your wake-up time and we will calculate the optimal bedtimes that align with your natural 90-minute sleep cycles — so you wake at the end of a cycle feeling refreshed rather than groggy.
Sleep occurs in 90-minute cycles. Waking in the middle of a cycle causes sleep inertia — that groggy, disoriented feeling. Waking at the end of a cycle feels natural and refreshed. This calculator works backwards from your alarm to find the ideal times to fall asleep.
We add your average sleep onset time (how long it typically takes to fall asleep) so results are personalised to you.
To wake at 7:00 AM, go to bed at:
★ Highlighted times provide optimal sleep duration (7.5–9 hrs)
Are you a Lion, Bear, Wolf, or Dolphin? Your chronotype — your biological sleep-wake preference — is largely genetic. Discover yours and find the schedule your body is wired for.
Sleep debt accumulates when you sleep less than your body needs. Calculate yours and see how many recovery nights are required to restore full cognitive function.
Find optimal bedtimes based on 90-min sleep cycles.
Open Tool → 🌙What time should you go to bed tonight?
Open Tool → 🦁Lion, Bear, Wolf, or Dolphin — what are you?
Open Tool → 💤How much sleep do you owe your brain?
Open Tool → 📓Printable daily sleep tracking worksheet (PDF).
Open Tool → 🧪20-question personalised sleep report.
Open Tool →A science-backed 7-night programme trusted by 50,000+ readers. Covers sleep hygiene, breathing techniques, supplement timing, and your personalised schedule.