Sleep Calculator

Recommended hours for the age group you select, then a labeled 90-minute cycle grid. An estimate, not a diagnosis.

Smart Tips

• The hour range is the result. The 90-minute rows are a labeled grid under it.

• Adults (26–64) and young adults (18–25) are 7–9 hours. Older adults (65+) are 7–8 hours.

• Six hours is 4 × 90 minutes. That block is outside the adult recommended range.

• NINDS says the first REM period is about 90 minutes after falling asleep. Cycles are not a fixed 90 minutes.

• A wake time only subtracts blocks from that clock. It is not a time-zone conversion.

• Sleeping less than the range is not fixed by landing on a cycle line.

The Formula

recommended hours = the NSF range for the age group
block hours = cycles × 1.5

NSF Recommended hours
Hirshkowitz et al., 2015, reaffirmed 2026

90 Minutes per labeled block
First REM about 90 minutes after sleep onset

7–9 Adults 26–64
Same range as young adults 18–25

7–8 Older adults 65+
9 hours is outside this range

A block is marked inside the range only when its hours sit between the published minimum and maximum, inclusive. 7.5 is inside 7–9. 6 and 9.0 for ages 65+ are not.

Key Insights

Hours come first

The hero number is the published range for the age group. The grid does not replace that range.

Labeled, not measured

The page cannot see sleep stages. Each row is cycles × 90 minutes, marked inside or outside the range.

Six hours is not the adult range

Four blocks are 6 hours. The adult recommendation is 7–9 hours. A cycle chart does not make 6 hours enough.

Not a clock-zone tool

Optional wake time is subtraction on a 24-hour clock. It does not convert time zones.

90-minute grid

Block	Hours
3 × 90 min	4.5 hours. Labeled block, not a sleep stage.
4 × 90 min	6 hours. Outside the adult 7–9 hour range.
5 × 90 min	7.5 hours. Inside the adult and older-adult ranges.
6 × 90 min	9 hours. Inside the adult range. Outside 7–8 for ages 65+.
1 × 90 min	1.5 hours. NINDS says the first REM period is about 90 minutes after falling asleep.

Medical Disclaimer

Estimate only: This page is an estimate, not a diagnosis, a lab test, or a treatment plan.

Not a sleep study: This is not a screen for insomnia, apnea, or depression. A short night is not corrected by a 90-minute grid.

Frequently Asked Questions

They are the National Sleep Foundation recommendations: newborns 14–17, infants 12–15, toddlers 11–14, preschoolers 10–13, school-aged children 9–11, teenagers 8–10, young adults and adults 7–9, and older adults 7–8. The Foundation reaffirmed those 2015 ranges on 10 June 2026.

Each row is a count of 90-minute blocks: 1.5, 3, 4.5, 6 hours, and so on, through 12 blocks. A row is marked inside the recommended range only when those hours fall inside the published minimum and maximum. NINDS says REM sleep first occurs about 90 minutes after falling asleep. Real cycles are not a fixed 90 minutes.

No. Six hours is 4 × 90 minutes, and the adult range is 7–9 hours. Five blocks are 7.5 hours, which is inside that range. The grid does not make a shorter night enough.

If you enter an hour from 0 to 23 and a minute from 0 to 59, each row also shows that clock minus the block length. 07:00 minus five blocks (450 minutes) is 23:30 the day before. Blank fields skip the clock. This is not a time-zone conversion.

The National Sleep Foundation review reaffirmed one range per life stage. It reported that the current science does not support separate sleep-duration recommendations for women and men. This page does not split the ranges by sex.

Recommended hours are the National Sleep Foundation ranges from Hirshkowitz and colleagues, Sleep Health, 2015, reaffirmed 10 June 2026, Sleep Duration Recommendations. The 90-minute label follows NINDS Brain Basics: Understanding Sleep, which says REM sleep first occurs about 90 minutes after falling asleep.

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Recommended hours

Enter values to calculate

Blocks in range

Block length

90-minute cycle grid

Note:The hours are the National Sleep Foundation range for the group you selected. The grid is labeled 90-minute blocks, not measured sleep stages. An estimate, not a diagnosis. Not a time-zone tool.