Sleep Cycle Calculator

Find suggested bedtimes or wake-up times using simple sleep-cycle timing and a fall-asleep buffer. Use it for quick planning and share the same setup with a URL.

All calculations run in your browser only; nothing is uploaded.

Use this page for bedtime and wake-up planning. It is not medical advice and it does not replace an alarm app.

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How to use this calculator

  1. 1. Choose whether you want bedtime suggestions from a wake-up target or wake-up suggestions from a bedtime.
  2. 2. Enter the time, then set the fall-asleep buffer and cycle length in minutes.
  3. 3. Compare the 4, 5, and 6 cycle options and pick the one that best matches your schedule.
  4. 4. Copy the URL if you want to reopen or share the same setup later.

Mode

Choose the time you want to wake up, then compare 4, 5, and 6 cycle bedtime options.

Use a fall-asleep buffer if you rarely fall asleep instantly. 15 minutes is a sensible planning default.
90 minutes is a common planning default. Adjust it only if you want a different internal assumption.

Suggested bedtime

Enter your time and assumptions to see the result.

When to use this page

Use this page when you want a quick bedtime or wake-up planning estimate based on editable assumptions.

Use the alarm tool if you need an actual alarm, and use Time Add if you only need generic duration math.

What this page does not do

How it’s calculated

The calculator converts your input time into minutes since midnight, then adds or subtracts the fall-asleep buffer and a fixed number of cycle-length blocks.

Each option uses the same formula with 4, 5, or 6 cycles. Results wrap around midnight and can show previous-day or next-day labels when needed.

Sleep duration is cycles × cycle length. Total time in bed adds the fall-asleep buffer on top of that duration.

FAQ

Why is 90 minutes the default?

It is a common planning assumption for a rough sleep-cycle estimate. The page lets you edit that number because people may prefer a different assumption.

Should I include the time it takes to fall asleep?

Yes. That is what the fall-asleep buffer is for. If you usually need around 15 minutes before you are asleep, keep the default or adjust it to match your habit.

Why can I still feel tired even if a time lines up with a cycle?

Real sleep quality depends on more than simple timing. Stress, illness, sleep debt, interruptions, and many other factors can affect how rested you feel.

Is this page medical advice?

No. It is a browser-based planning tool only. If sleep problems affect your health or daily life, use professional medical advice as the main reference.

What should I use if I need an actual alarm?

Use the Online Alarm tool. This page only suggests times; it does not ring, notify, or keep a running alarm state.

Next steps

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Comments

Share planning tips, bedtime routine ideas, or how you use the cycle assumptions in practice.