Sleep Calculator

Find the best time to fall asleep so you wake up at the end of a natural sleep cycle. Uses 90-minute cycles + 15 minutes to fall asleep.

⚡ Fast & mobile-friendly

🧠 Sleep cycle based

🔗 Optional sharing

Enter your details

Choose the time you want to wake up. The calculator will suggest several optimal bedtimes based on sleep cycles.

Wake-up time

Desired sleep (hours, optional)

Target sleep cycles (optional)

Your result will appear here

Enter your wake-up time and click “Calculate” to see multiple recommended bedtimes.

This tool is for general sleep planning only and does not replace medical advice. If you have trouble sleeping, talk to a healthcare professional.

🧮 How it works

The sleep cycle method

During the night, your brain cycles through light sleep, deep sleep, and REM sleep. On average, one full cycle lasts about 90 minutes.

Waking up between cycles (in deep sleep) feels terrible. Waking up at the end of a cycle feels lighter and more refreshed.

Formula

We calculate your bedtime like this:

Bedtime = Wake-up time − (Number of cycles × 90 min) − 15 min (to fall asleep)

Cycle reference

Cycles	Hours of sleep	Typical use
3 cycles	4.5 hours	Short night / emergency
4 cycles	6.0 hours	Minimum for many adults
5 cycles	7.5 hours	Common recommended target
6 cycles	9.0 hours	When you need extra recovery

Example

Suppose you want to wake up at 6:30 AM. Here are some possible bedtimes:

3 cycles (4.5h): 1:45 AM
4 cycles (6.0h): 12:15 AM
5 cycles (7.5h): 10:45 PM
6 cycles (9.0h): 9:15 PM

For most adults, 5 cycles (7.5 hours) is a great starting point.

📚 Interpretation

How to interpret your result

The calculator shows you several bedtimes corresponding to different numbers of sleep cycles.

General guidance

3 cycles (4.5h): Use only when you have no choice. You may still feel tired.
4 cycles (6h): OK for some adults, but not ideal for long-term health.
5 cycles (7.5h): A strong target for most adults.
6 cycles (9h): Helpful when you’re sick, stressed, or exhausted.

Practical tips

Pick a bedtime you can realistically stick to most days.
Avoid screens and bright light 30–60 minutes before bed.
Keep your bedroom cool, dark, and quiet.
Try going to bed and waking up at the same times every day.

❓ FAQ

Frequently asked questions

Is 7.5 hours of sleep enough?
Many adults feel their best around 7–8 hours, but some need more and some less. Use this as a starting point and adjust based on your energy and mood.
Do sleep cycles always last 90 minutes?
No. In reality, cycles range from about 80–120 minutes. 90 minutes is a simple, widely used average.
What if I wake up during a cycle?
You may feel groggy or disoriented. Try adjusting your bedtime by 15–30 minutes next night to hit a better boundary.
Does this work for naps?
Yes — a 20–30 minute power nap or a full 90-minute cycle can both be helpful. This calculator focuses on full-night sleep patterns.
Should children use this calculator?
Children and teens generally need more total sleep and different schedules. Talk to a pediatrician for age-specific recommendations.

MaximCalculator is designed for easy, everyday calculations. Always listen to your body and consult a healthcare professional for persistent sleep issues.