HRV baseline calculator
Compare today’s HRV with your own recent readings, average and range.
Bedtime calculator
Work backward from your alarm, or forward from bedtime, to make room for the sleep you want.
Your sleep plan
Example valuesClock arithmetic only: daylight saving changes and overnight awakenings are not included.
No account needed. Calculations happen in your browser; your entries are not saved or sent to Century.
Example · Your planned bedtime
22:45
Your schedule allows 8h 0m asleep and 15 minutes to fall asleep.
- Time in bed
- 8h 15m
- Previous day
- Bedtime
22:45Bedtime23:00Planned sleep starts07:00Wake-up time
How it’s calculated
Bedtime = wake-up time − desired sleep duration − time to fall asleep. Wake-up time = bedtime + time to fall asleep + desired sleep duration. Times wrap across midnight using a 24-hour clock. This is schedule arithmetic, not a prediction of your sleep stages, sleep quality or personal sleep need. It does not assume fixed 90-minute cycles.
Reference: NHLBI: Sleep phases and stages
For general wellness information. This tool does not diagnose health conditions or replace medical advice.
Related tools
Give your sleep target a place in your schedule
Calculate bedtime from a fixed alarm
Enter when you need to wake up, the hours you want to spend asleep and how long you expect to take to fall asleep. The bedtime result is when to get into bed, not the instant sleep begins.
Decimal hours work for the sleep target: 7.5 means seven hours and thirty minutes. Use a 24-hour clock for the fixed time. If the result crosses midnight, the day label makes that visible.
Calculate wake-up time from bedtime
Switch to Wake-up time if bedtime is your fixed point. The tool adds time to fall asleep and your chosen sleep duration. The visual timeline separates time in bed before sleep, planned sleep and the alarm.
This planner has no date or location input. It cannot account for daylight saving changes or travel between time zones. On those nights, check actual elapsed time separately.
Plan enough time without promising perfect cycles
A sleep target is a choice for this calculation, not a measurement of your biological sleep need. Overnight awakenings also reduce time asleep and are not estimated here.
Sleep cycles vary, so fixed 90-minute blocks cannot guarantee an ideal waking moment. This tool focuses on a transparent schedule. Century can connect available wearable sleep history with your ongoing recovery trends.
Frequently asked questions
What time should I go to bed to wake up at 7 am?
For eight hours asleep and 15 minutes to fall asleep, plan to get into bed at 22:45 the previous day. Change the sleep target and time to fall asleep to match the schedule you want to plan.
Does this calculator use 90-minute sleep cycles?
No. Sleep cycles vary within a night and between people. A fixed cycle length cannot predict the exact moment you will leave deep sleep. This tool calculates a schedule from your chosen sleep duration.
Should I count time to fall asleep as sleep?
No. Time to fall asleep is added separately to the time you plan to spend asleep. Eight hours of sleep plus 15 minutes to fall asleep requires eight hours and 15 minutes in bed, before allowing for any overnight awakenings.
Can I calculate a wake-up time instead?
Yes. Choose Wake-up time, enter when you plan to get into bed, and choose your sleep target and time to fall asleep. The result shows the planned wake-up time and whether it falls on the following day.
Does this tell me how much sleep I need?
No. Your sleep target is an input. The calculator does not measure biological sleep need or guarantee you will feel refreshed. It also does not subtract time spent awake during the night.
What happens when clocks change for daylight saving time?
This tool uses ordinary clock arithmetic without a date or time zone. On a clock-change night, the actual elapsed sleep opportunity can differ by an hour. Check the local clock change when planning that night.