Bedtime & Sleep Cycle Calculator

Find Your Perfect Bedtime & Feel Energized Tomorrow

The smartest sleep calculator — personalized for real life.

Calculate My Bedtime
  • · No sign-up
  • · No data stored
  • · Works offline
  • 🧬
    Built on real cycles90-min REM & deep sleep math
  • 🎯
    Personalized to youcaffeine, kids, jet lag, age
  • ⚡
    Energy forecastknow how tomorrow will feel
  • 🔒
    100% privatenothing leaves your device

Your sleep details

We use your real-world factors to predict the best bedtime tonight.

How tired do you feel right now?
Neutral
Quick factors

How it works

Built around the 90-minute sleep cycle

Your brain doesn't sleep flat. It rolls through 4–6 cycles of light, deep, and REM sleep — each about 90 minutes. Wake up at the end of a cycle and you'll feel sharp. Wake up mid-cycle and you'll feel groggy, no matter how long you slept.

Most calculators stop there. Sleep Forecaster also factors in the things that actually mess with your night: caffeine, kids, shift work, jet lag, and how wired you feel right now.

  • 1
    Pick your wake time

    We work backward from when you actually need to be up.

  • 2
    Tell us about your day

    Age, energy, caffeine, kids, shift work, travel — all change the math.

  • 3
    Get your bedtime + energy score

    Two ideal options, a fall-asleep buffer, and tomorrow's energy forecast.

Frequently asked questions

What time should I go to bed if I want to wake up at 7 AM?

To wake up refreshed at 7:00 AM, be in bed by 9:46 PM for 6 full sleep cycles (9 hours) or 11:16 PM for 5 cycles (7.5 hours). Both options already account for the ~14 minutes it usually takes to fall asleep — so you'll be in deep sleep right on schedule.

How long is one sleep cycle?

A full sleep cycle averages around 90 minutes and includes light, deep, and REM stages. Waking at the end of a cycle leaves you feeling more energized than waking mid-cycle.

Is the bedtime calculator free?

Yes. It's 100% free, requires no account, and stores no personal data. Everything runs in your browser.

How many hours of sleep do I really need?

Most adults do best on 7–9 hours. Teens need 8–10. Sleeping in full 90-minute cycles is why 7.5 or 9 hours often feels better than a flat 8.