CALCULATOR

Sleep Calculator

Bedtime or wake time in 90 minute cycles, with the honest caveat that total duration matters more than cycle timing.

Suggested times

–

Best option–

6 cycles, 9 hours–

5 cycles, 7.5 hours–

4 cycles, 6 hours–

3 cycles, 4.5 hours–

Five to six cycles covers the seven to nine hours most adults need. Waking between cycles tends to feel easier than waking mid-cycle, though total duration matters more than perfect timing.

25 free calculators, all in one placeTDEE, macros, body fat, recomp, one rep max, pace, creatine and more.

Explore all calculators →

Sleep cycles and timing

Sleep runs in cycles averaging about 90 minutes, moving through light sleep, deep sleep and REM. Waking at the end of a cycle, in lighter sleep, generally feels easier than being woken mid-cycle from deep sleep.

This calculator works backwards from your wake time, or forwards from bedtime, in 90 minute blocks, adding the time it takes you to fall asleep. Five or six cycles covers the seven to nine hours most adults need.

Two honest caveats. Cycle length varies between roughly 70 and 110 minutes and changes across the night, so these times are guides rather than precise targets. And total sleep duration matters considerably more than perfect cycle timing, so do not sacrifice an hour of sleep to hit a cycle boundary.

Frequently asked questions

How long is a sleep cycle?

About 90 minutes on average, varying between 70 and 110 minutes and lengthening later in the night.

Is it better to sleep 6 or 7 hours?

Seven, in almost all cases. Total duration matters more than landing on a cycle boundary.

Why do I feel worse after more sleep?

Usually waking from deep sleep mid-cycle, or sleep inertia. Irregular timing is a more common cause than duration.

Does sleep affect fat loss?

Substantially. At identical calorie deficits, short sleepers lost about half as much fat and more lean mass in controlled research.

Sources

Carskadon MA, Dement WC. Normal Human Sleep: An Overview. Principles and Practice of Sleep Medicine.
Hirshkowitz M et al. National Sleep Foundation sleep time duration recommendations. Sleep Health, 2015.
Nedeltcheva AV et al. Insufficient sleep undermines dietary efforts to reduce adiposity. Annals of Internal Medicine, 2010.
Centers for Disease Control and Prevention. Sleep and Sleep Disorders. cdc.gov
National Institutes of Health, Office of Dietary Supplements. Nutrient fact sheets. ods.od.nih.gov
NHS. Nutrition and health guidance. nhs.uk
US Departments of Agriculture and Health and Human Services. Dietary Guidelines for Americans, 2025-2030. dietaryguidelines.gov

More tools: all calculators · Full Plan · Recomp · Body fat · Macros · Cheapest whey per 20 g

General information, not medical advice. Consult a qualified professional before changing your diet, especially with a medical condition.