# Sleep Calculator

URL: https://speedycalculator.com/calculators/health/sleep/
Last updated: 2026-10-25

> The sleep calculator suggests bedtimes that let you wake at the end of a sleep cycle, assuming 90-minute cycles and about 15 minutes to fall asleep. Waking between cycles can help you feel less groggy.

## Inputs

- Wake-up hour (0–23)
- Wake-up minute
- Minutes to fall asleep

## Results

- Bedtime for 6 cycles (9 h)
- Bedtime for 5 cycles (7.5 h)
- Bedtime for 4 cycles (6 h)

## Formula

```
Bedtime = wake time − (cycles × 90 min) − 15 min
```

## Explanation

Sleep runs in cycles of roughly 90 minutes. Most adults need 7–9 hours, which is about five to six cycles.

### How to use the Sleep Calculator

- **Wake-up hour (0–23)**
- **Wake-up minute**
- **Minutes to fall asleep**

Results update as you type, and every field accepts the units shown in its menu.

### How it works

Starting from your wake-up time, the calculator counts back whole cycles plus the time it takes to fall asleep.

### Inputs explained

FieldWhat to enterWake-up hour (0–23)A numberWake-up minuteA numberMinutes to fall asleepA number

### What each result means

- **Bedtime for 6 cycles (9 h)** = [Wake time (hours)] - 9 - [Minutes to fall asleep]÷60
- **Bedtime for 5 cycles (7.5 h)** = [Wake time (hours)] - 7.5 - [Minutes to fall asleep]÷60
- **Bedtime for 4 cycles (6 h)** = [Wake time (hours)] - 6 - [Minutes to fall asleep]÷60

*Health note: this calculator is for education and screening only and is not a diagnosis or treatment advice. Discuss your results with a qualified clinician.*

## Worked example

Inputs — Wake-up hour (0–23): 7; Wake-up minute: 0; Minutes to fall asleep: 15.

Results — **Bedtime for 6 cycles (9 h) = 21:45**; Bedtime for 5 cycles (7.5 h) = 23:15; Bedtime for 4 cycles (6 h) = 00:45.

## FAQ

**Are all sleep cycles 90 minutes?**
They range from about 70 to 120 minutes and change through the night.

**How much sleep do adults need?**
At least 7 hours, according to sleep medicine societies.

**What formula does the Sleep Calculator use?**
Bedtime = wake time − (cycles × 90 min) − 15 min.


## Sources

- [American Academy of Sleep Medicine – Sleep duration recommendations](https://aasm.org/resources/pdf/pediatricsleepdurationconsensus.pdf)