If I wake up at 9:00, what time should I go to bed?
The short answer
To wake at 9:00 with 8 hours of sleep, be in bed by 00:45. That allows about 15 minutes to fall asleep. Most adults need 7 to 9 hours, so anywhere from 23:45 to 01:45 can be right for you.
Each time includes 15 minutes to fall asleep. If you usually drop off faster or slower, move it by the difference.
What about sleep cycles?
Many calculators count back in 90-minute cycles. Cycles vary from person to person and from night to night, so a fixed 90 minutes is a rough guide at best. Getting enough sleep at a steady time matters more than landing on a cycle boundary.
When 9:00 is earlier than usual
If you normally get up later, moving bedtime earlier by the full difference in one night rarely works. Going to bed up to an hour earlier the night before is more realistic, and a steady wake time through the week makes early starts easier.
Let your alarm do the maths
First Thing plans your bedtime from tomorrow's alarm every night, eases it earlier before an early start, and tells you when to wind down.

Other wake-up times
Questions
How much sleep do adults need?
The NHS says most adults need between 7 and 9 hours a night. The right amount for you is the one that leaves you awake through the day without caffeine doing the work.
Is it bad to sleep 6 hours if I wake at 9:00?
An occasional short night is fine. Regularly sleeping less than 7 hours is linked to feeling tired and less alert, so aim for the earlier bedtimes above most nights.
What time should I go to bed if I wake up at 9:00 and have a flight?
Work back from the alarm, not the flight. Our early flight calculator gives you the alarm, then use this page.