Sleep calculator: everything you need to know about it

published 27 March 2017

Here's everything you need to know, from the length of a complete sleep cycle to when you should be getting some shut-eye…

We all follow a similar sleep pattern, with a full night’s sleep broken into multiple sleep cycles, alternating between transitional, light and deep sleep. Although it may seem trivial, waking up at the wrong stage of a sleep cycle can have a dramatic effect.

Waking up at the end of a 90-minute sleep cycle, when in a light sleep, will leave you feeling refreshed and rejuvenated. Waking up during the wrong stage of a sleep cycle, when in a deep sleep, however, can leave you feeling exhausted.

When in a deep sleep, your body temperature decreases, your heart rate slows and your muscle activity winds down – waking up in that state can be very disorientating, and often when you wake up confused or feeling groggy, it is down to waking up at the wrong stage of your sleep cycle rather than sleep deprivation.

The trick is ensuring that you wake up at the right stage of your sleep cycle. That’s where using a sleep calculator comes in.

What is a sleep calculator?

A sleep calculator is a generator that shows you the best time to go to sleep and set your alarm in the morning. Using a formula based on the body’s natural rhythms, it will provide you with a selection of times to set your alarm clock at, making sure you don’t interrupt a sleep cycle and therefore guaranteeing that you wake up in the morning feeling energised and refreshed.

How many sleep cycles are in a full night’s sleep?

A full night’s sleep is usually made up of 5-6 sleep cycles, each being 90 minutes long. The sleep calculator will ensure that you will rise between these sleep cycles.

What time should I go to bed if I want to wake up at 6.30am?

If you want to wake up feeling refreshed and awake at 6.30am you should go to bed at one of the following times: 9.15pm/ 10.45pm/ 12.15am/ 1.45am/ 3.15am/ 4.45am

What time should I go to bed if I want to wake up at 7am?

If you want to wake up feeling refreshed and awake at 7am you should go to bed at one of the following times: 9.45pm/ 11.15pm/ 12.45am/ 2.15am/ 3.45am/ 5.15am

What time should I go to bed if I want to wake up at 8am?

If you want to wake up feeling refreshed and awake at 8am you should go to bed at one of the following times: 10.45pm/ 12.15am/1.45am/ 3.15am/ 4.45am/ 6.15am

How long does it take to fall asleep?

It takes the average human about 15 minutes to fall asleep so be aware of that when calculating the times you should go to sleep and wake up.

Jenny Proudfoot is an award-winning journalist, specialising in lifestyle, culture, entertainment, international development and politics. She has worked at Marie Claire UK for seven years, rising from intern to Features Editor and is now the most published Marie Claire writer of all time. She was made a 30 under 30 award-winner last year and named a rising star in journalism by the Professional Publishers Association.