Sleep Calculator

Free sleep calculator based on 90-minute sleep cycles. Enter your bedtime to see optimal wake times, or enter your wake time to see when to go to bed. Accounts for 15 minutes to fall asleep. Includes age-based sleep recommendations and sleep quality tips.

What time are you going to bed?

Suggested Wake-Up Times

3:15 AM

Minimal3 cycles4h 45m

4:45 AM

Fair4 cycles6h 15m

Recommended

6:15 AM

Good5 cycles7h 45m

Recommended

7:45 AM

Excellent6 cycles9h 15m

9:15 AM

Excellent7 cycles10h 45m

10:45 AM

Excellent8 cycles12h 15m

Calculations include approximately 15 minutes to fall asleep. Each sleep cycle lasts about 90 minutes. Waking between cycles (rather than in the middle of one) helps you feel more refreshed and alert.

Sleep Cycle Stages (One ~90-min Cycle)

Awake

REM/N1

Deep

0 min15 min30 min45 min60 min75 min90 min

Awake

Light (N1)

Light (N2)

Deep (N3)

REM

N1 (Light Sleep): Transition phase between wakefulness and sleep. Lasts 1-5 minutes. Easy to wake from.

N2 (Light Sleep): Body temperature drops, heart rate slows. Makes up about 50% of total sleep time.

N3 (Deep Sleep): Most restorative stage. Body repairs tissues, builds bone and muscle. Difficult to wake from.

REM (Rapid Eye Movement): Brain activity increases, dreaming occurs. Essential for memory consolidation and learning.

Sleep Recommendations by Age

Age Group	Age Range	Recommended Sleep	Cycles
Newborn	0-3 months	14-17 hours	9-11
Infant	4-11 months	12-15 hours	8-10
Toddler	1-2 years	11-14 hours	7-9
Preschool	3-5 years	10-13 hours	7-9
School-age	6-13 years	9-11 hours	6-7
Teenager	14-17 years	8-10 hours	5-7
Young Adult	18-25 years	7-9 hours	5-6
Adultselected	26-64 years	7-9 hours	5-6
Senior	65+ years	7-8 hours	5-5

Adult (26-64 years)

0h7-9h recommended17h

Source: National Sleep Foundation (NSF) guidelines. Individual needs may vary. Click a row to highlight it.

Tips for Better Sleep

Keep a Consistent Schedule

Go to bed and wake up at the same time every day, even on weekends. This reinforces your body's circadian rhythm.

Create a Relaxing Routine

Wind down 30-60 minutes before bed. Avoid screens, read a book, take a warm bath, or practice deep breathing.

Optimize Your Environment

Keep your bedroom cool (60-67F / 15-19C), dark, and quiet. Consider blackout curtains and earplugs.

Limit Caffeine & Alcohol

Avoid caffeine at least 6 hours before bedtime. While alcohol may help you fall asleep, it disrupts REM sleep.

Exercise Regularly

Regular physical activity can help you fall asleep faster and enjoy deeper sleep, but avoid intense exercise 2-3 hours before bed.

Manage Light Exposure

Get bright light exposure during the day and reduce blue light from screens in the evening to support melatonin production.

How This Calculator Works

90-Minute Sleep Cycles

A full sleep cycle lasts approximately 90 minutes and progresses through light sleep (N1, N2), deep sleep (N3), and REM sleep. Waking at the end of a complete cycle (during light sleep) helps you feel more refreshed than waking during deep sleep.

15 Minutes to Fall Asleep

The average healthy adult takes about 10-20 minutes to fall asleep (sleep onset latency). This calculator uses 15 minutes as a reasonable average, so your actual sleep time may vary.

Optimal Number of Cycles

Most adults need 5-6 complete sleep cycles (7.5 to 9 hours) per night. Getting fewer than 4 cycles regularly is associated with impaired cognitive function, mood changes, and weakened immune response.

How to Use Sleep Calculator

1Choose mode: 'When to wake up' or 'When to go to bed'.
2Enter your bedtime or desired wake time.
3View recommended times based on sleep cycles.
4Select the option that gives you enough cycles.

Frequently Asked Questions

How does the sleep calculator work?▾

It calculates based on 90-minute sleep cycles. Waking between cycles (rather than mid-cycle) helps you feel more refreshed.

How many hours of sleep do I need?▾

Adults need 7-9 hours (4-6 sleep cycles). Teens need 8-10 hours. Children need 9-12 hours depending on age.

Why do I feel tired after 8 hours of sleep?▾

You may be waking mid-cycle. Try adjusting your wake time by 15-30 minutes to align with a cycle boundary.

About Sleep Calculator

NexTool's Sleep Calculator is completely free to use with no sign-up required. Your data is processed directly in your browser and never sent to our servers, ensuring complete privacy and instant results.

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