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How Much Sleep Do I Need?

A 35-year-old adult needs about 7-9 hours of sleep a night, with 8 hours as the typical target.

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Same equations the textbooks use — just way less awkward. Pop in your stats and I'll tell you what the number actually means for you.

Try a scenario

Click to load — tweak from there.

Inputs

Result

Min recommended hours

7

Max recommended hours

9

Ideal bedtime hour (24h, 5 cycles)

22

Ideal bedtime minute

45

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How to use this

  1. 1Enter age (years).
  2. 2Enter wake-up hour (24h).
  3. 3Enter wake-up minute.
  4. 4Read your min recommended hours on the right — it updates as you type.
  5. 5Hit Share to keep the scenario or send it to someone.

About this calculator

Sleep needs vary primarily by age, with recommendations from the National Sleep Foundation ranging from 14-17 hours for newborns down to 7-9 hours for adults. This calculator maps your age to the recommended sleep range and, if given a wake time, computes ideal bedtimes accounting for 90-minute sleep cycles.

FormulaRecommended hours are looked up by age band. Bedtime Options = Wake Time − (n × 90 minutes) − 15 min to fall asleep, for n = 4,5,6 cycles.

Worked example

Using the values the calculator loads with:

Inputs

  • Age: 35 years
  • Wake-up hour (24h): 6
  • Wake-up minute: 30

Results

  • Min recommended hours: 7
  • Max recommended hours: 9
  • Ideal bedtime hour (24h, 5 cycles): 22
  • Ideal bedtime minute: 45

What each field means

Inputs

Age (years)
The age used in the calculation, measured in years. Starts at 35 years so you have a working example on load. Accepted range: 0–100 years.
Wake-up hour (24h)
The wake-up hour (24h) used in the calculation. Starts at 6 so you have a working example on load. Accepted range: 0–23.
Wake-up minute
The wake-up minute used in the calculation. Starts at 30 so you have a working example on load. Accepted range: 0–59.

Results

Min recommended hours
Returned as a whole number and shown as the headline result. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
Max recommended hours
Returned as a whole number. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
Ideal bedtime hour (24h, 5 cycles)
Returned as a whole number. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
Ideal bedtime minute
Returned as a whole number. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.

FAQ

How much sleep do I need?

A 35-year-old adult falls in the 18-64 age band, which is recommended 7-9 hours of sleep a night by the National Sleep Foundation, with most adults doing best around 8 hours.

Why do sleep needs decrease with age?

Sleep architecture changes across the lifespan — infants and children need more sleep to support rapid brain and physical development, while older adults typically need slightly less total sleep though sleep quality often becomes more important.

What are sleep cycles and why do they matter for bedtime?

A full sleep cycle is about 90 minutes; waking up mid-cycle (during deep sleep) causes grogginess, so timing bedtime to complete whole cycles before your alarm — typically 5 or 6 cycles — helps you wake up feeling more rested.

Is more sleep always better?

Not necessarily — consistently sleeping well beyond 9-10 hours for adults has been associated in some studies with underlying health issues, so both too little and unusually excessive sleep can be worth discussing with a doctor.

Accuracy and limitations

  • Population formulas describe averages; individual bodies vary, especially at the extremes of height, age, or muscle mass.
  • Results do not account for medical conditions, medication, or pregnancy.
  • Use this as a directional reference, not a diagnosis — talk to a clinician before acting on it.

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A 170 lb moderately active adult should drink about 100 ounces (12.5 cups) of water a day.

How Many Hours Until My Deadline?

A deadline 6 days away has 144 total hours remaining, or about 48 working hours if you work 8-hour weekdays.

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APA
RevenueLab. (2026). How Much Sleep Do I Need?. Retrieved from https://www.revenuelab.fyi/toolbox/how-much-sleep-do-i-need
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