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Sleep Calculator

What time should I go to bed?

Choose when you want to wake up (or go to bed) and how much sleep you are aiming for, and see the other time.

One Click Answers · Sleep Calculator
oneclickanswers.com/sleep-calculator · Printed
About this tool & how to use it

What it does

Finds the bedtime for the wake-up time you want (or the wake time for your bedtime) from the hours of sleep you choose and your time to fall asleep. It shows the CDC range for your age group as a reference, not a target.

How to use it

  1. Pick whether you know your wake-up time or your bedtime, and enter it.
  2. Choose the hours of sleep you are aiming for and the minutes it usually takes you to fall asleep.
  3. Read the bedtime or wake time first, then the other options for 6, 7, 8 and 9 hours.

Use a time such as 7:00 AM.

This is your choice. The CDC ranges are shown below for reference.

One click answer

Your answer will appear here.

Fill in the form and your answer appears here as you type.

Assumptions

  • The hours of sleep and the minutes to fall asleep are the ones you enter.
  • Sleep does not run in exact blocks, so treat the time as a starting point rather than a rule.
  • The CDC age-group figures (CDC About Sleep page, read 2026-10-04) are shown as reference only.

Printed from oneclickanswers.com. Results are estimates based on what was entered; see the assumptions above.

How it works

Bedtime = wake time - the hours of sleep you chose - the minutes to fall asleep. Wake time = bedtime + the same two amounts, counted across midnight.

Waking at 7:00 AM after 8 hours with 15 minutes to fall asleep gives 7:00 AM - 8 hours - 15 minutes = 10:45 PM.

The CDC range for your age group is printed beside the answer as a reference. The page does not say whether your choice is right for you.

Formulas and details
  • Bedtime = wake time - sleep - minutes to fall asleep.
  • Wake time = bedtime + minutes to fall asleep + sleep.

Assumptions

  • The hours of sleep and the minutes to fall asleep are the ones you enter.
  • Sleep does not run in exact blocks, so treat the time as a starting point rather than a rule.
  • The CDC age-group figures (CDC About Sleep page, read 2026-10-04) are shown as reference only.

Example

Input: The starting values already in the form

Result: To wake up at 7:00 AM after 8 hours of sleep, be in bed by about 10:45 PM. That allows 15 minutes to fall asleep first, so you would be in bed for 8 hours 15 minutes.

Questions

Does this use 90-minute sleep cycles?

No. Cycle length differs from person to person and from night to night, so the page uses plain clock arithmetic and the hours you choose instead of claiming exact cycles.

How much sleep do I need?

The page shows the CDC range for the age group you pick, as a reference. How much sleep a person needs is a question for them and their doctor.

Last reviewed 2026-10-04.

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