How Many Calories Do You Burn Sleeping? Calculator & Science

The content on this page is for general informational and educational purposes only and is not intended as medical advice. Always consult a qualified healthcare provider before making changes to your health or fitness regimen.

Eight hours in bed can feel like the least active part of your day. Yet your body still has an energy bill—even when you are completely unaware of it.

You burn roughly 50 calories per hour sleeping, or about 400 calories over eight hours, as a general reference—not a personalized measurement. Your actual expenditure depends on body size, body composition, and resting metabolism. According to the Sleep Foundation, sleep uses energy because your brain stays active and essential functions such as breathing and circulation continue.

The useful number is less about what happens on your pillow and more about your body's baseline energy needs. That distinction also explains why staying awake longer is not a weight-loss shortcut.

Sleep calorie calculator: estimate your overnight burn

A common rough calculation is:

Sleep calories ≈ (daily resting calories ÷ 24) × hours asleep × 0.85.

The 0.85 factor assumes sleeping expenditure is about 15% below the waking resting rate. Medical News Today presents it as a rough estimate based on basal metabolic rate (BMR). It is not a universal physiological constant or a validated personalized sleep measurement.

Quick estimate table

These are calculated examples using that shortcut—not measured averages by weight or sex. “Calories” here means dietary kilocalories, or kcal.

Values are rounded independently. The table shows why a single “calories burned in eight hours” answer cannot fit everyone.

Spreadsheet-ready calculation

With daily resting calories in cell A2 and hours actually asleep in B2, the calculation is:

=ROUND((A2/24)*B2*0.85,0)

For example, 1,600 resting calories/day and eight hours asleep gives approximately 453 calories. That is the result of the assumptions—not proof that you burned precisely 453 calories.

Time in bed and time asleep are different inputs. This formula estimates the sleeping portion only; it does not separately calculate periods spent awake in bed.

How to estimate the resting calories used in the formula

Basal metabolic rate (BMR) describes energy use under strict basal testing conditions. Resting metabolic rate (RMR) is a closely related measure obtained under less restrictive conditions. Neither is your complete daily calorie expenditure. BodySpec's BMR calculator guide explains the distinction and common equation inputs.

Mifflin–St Jeor: an estimate from height, weight, and age

The commonly used rounded equations estimate resting energy expenditure:

• Male equation: RMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age(years) + 5
• Female equation: RMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age(years) − 161

These are rounded forms of the equation published in the foundational study by Mifflin et al. (1990). Pounds divided by 2.2046 gives kilograms; inches multiplied by 2.54 gives centimeters. The male/female categories reflect the original equation framework and may not adequately represent every person's physiology.

Worked example: For a hypothetical 35-year-old woman weighing 70 kg and measuring 165 cm:

RMR = 700 + 1,031.25 − 175 − 161 = 1,395.25 kcal/day

Eight-hour sleep estimate = (1,395.25 ÷ 24) × 8 × 0.85 ≈ 395 kcal

Lean-mass-based equations: a different input, not guaranteed accuracy

Two commonly used alternatives incorporate non-fat tissue mass:

Both equations are discussed in research comparing predicted and measured resting expenditure in weightlifters (Joseph et al., 2017).

Knowing your lean mass gives you another way to estimate resting calories, but it does not make the answer exact. In that small study of 30 male weightlifters from India, all eight tested equations predicted fewer resting calories than researchers actually measured, including the lean-mass-based ones.

For your own calculation, the takeaway is simple: body composition adds useful context, not a guarantee of accuracy. Applying a rough sleep adjustment adds another layer of uncertainty.

Why your body burns calories during sleep

Sleeping is not the same as shutting down. The energy estimate reflects ongoing essential functions—not exercise performed without moving.

Several factors explain differences between people and nights:

• Body size and composition: Larger bodies generally need more resting energy. Muscle contributes, but organs and other tissues also matter.
• Sleep duration: More hours asleep means more energy used during that sleeping period—not necessarily more energy used over the entire day.
• Sleep stages: Brain activity and metabolism change across REM (rapid eye movement) and non-REM sleep.
• Health and physiology: Hormonal conditions and other health factors can alter resting energy needs.

Does REM sleep burn more calories?

According to the Sleep Foundation, REM sleep generally involves more brain activity and higher energy expenditure than deep, slow-wave sleep. But the difference is not a practical calorie-control lever: a normal night includes several necessary stages, not one stage to maximize for fat loss.

Does metabolism automatically slow down in middle age?

Not in the simple way that phrase suggests. A large study found that daily energy expenditure adjusted for body composition was broadly stable from ages 20 to 60, before declining in later adulthood (Pontzer et al., 2021).

That was not a sleeping-calorie study, and it does not mean everyone burns the same amount throughout adulthood. It helps separate the effects of aging from differences in body size and composition. An age-based equation remains an estimate, not proof that a birthday caused your metabolism to slow.

The sleep-deprivation paradox: awake longer, eating more

It sounds logical: if sleep saves energy, staying awake should burn more. In controlled experiments, that first part is true—but it leaves out eating behavior.

In a small laboratory study of seven healthy young adults, a night of total sleep deprivation increased 24-hour energy expenditure by about 7% compared with a normal sleep schedule (Jung et al., 2011).

A separate study had 16 adults live in a research facility while researchers compared five-hour with nine-hour sleep opportunities. During restricted sleep, daily expenditure increased by about 5%, but food intake increased by approximately 6%. Participants ate more than they needed to maintain their weight and gained an average 0.82 kg during the restricted-sleep condition (Markwald et al., 2013).

That short-term scale change should not be interpreted as 0.82 kg of body fat. The study shows how extra eating can outpace extra calorie burn—not what will inevitably happen to you after a bad week of sleep.

What newer research adds

In a 2022 randomized trial of 80 adults with overweight who habitually slept less than 6.5 hours nightly, the sleep-extension group increased sleep by about 1.2 hours per night. Their estimated daily energy intake fell by approximately 270 calories relative to controls, without a significant change in total expenditure (Tasali et al., 2022).

The intervention lasted two weeks, so it does not establish guaranteed long-term weight loss. Its useful contribution is showing that the sleep–weight relationship is not simply about burning more calories overnight.

Is it all hunger hormones?

Ghrelin helps signal hunger; leptin signals energy availability and contributes to fullness; PYY is a gut hormone that also helps signal fullness. In the Markwald experiment, people ate extra food even though their hormone signals suggested they had already taken in enough energy: leptin and PYY rose, while ghrelin fell (Markwald et al., 2013).

A 2025 review combining six randomized trials also found no clear overall change in leptin or ghrelin after sleep deprivation. The researchers noted that the evidence was limited and the studies differed in how they tested sleep loss (Gresser et al., 2025).

For you, the important point is that appetite is more complicated than a single hormone switch. The claim that poor sleep always raises one hormone and lowers another is too neat, and a calorie calculator cannot diagnose a hormonal problem.

More calories burned while awake does not automatically translate into better weight management.

Can you meaningfully increase calorie burn while sleeping?

The overnight number is mostly a reflection of baseline physiology, not a separate fitness goal. Body composition matters to energy needs, but claims about dramatically “boosting metabolism overnight” exceed what these estimates can establish.

Likewise, a cool bedroom is a sleep-comfort measure—not a reliable fat-loss intervention. The National Heart, Lung, and Blood Institute (NHLBI) recommends a quiet, cool, dark bedroom, a consistent schedule, and generally 7–9 hours of sleep for adults; it does not prescribe a below-67°F calorie-burning threshold.

For calorie accounting, sleeping expenditure is already part of total daily energy expenditure (TDEE). Adding a sleep estimate on top of an existing full-day estimate would double-count it. BodySpec's TDEE explainer explains how resting needs, movement, and digestion fit together; the daily calorie-burn guide provides broader adult reference ranges.

What a BodySpec DEXA scan adds

DEXA is a gold-standard method for practical body composition assessment, providing estimates of fat mass, lean soft tissue, and bone mineral content, including regional measurements. A 2024 review describes its accuracy, reproducibility, and uses beyond weight or BMI alone (Kim, 2024).

That helps distinguish changes in fat from changes in lean tissue that scale weight alone cannot explain. However:

• Lean soft tissue is not identical to skeletal muscle. It includes water, organs, and other non-fat soft tissues.
• Fat-free mass includes bone mineral as well as lean soft tissue. Those terms are not automatically interchangeable inputs.
• DEXA does not directly measure RMR or sleeping calorie expenditure. A metabolic number calculated from composition remains an estimate.

BodySpec's body composition explainer provides more context on those measurements. A scan can characterize the body behind a calorie estimate; it cannot validate exactly how many calories one night's sleep used.

Frequently asked questions

How many calories do you burn sleeping for eight hours?

About 400 calories is a common reference estimate. With the rough 0.85 calculation, someone with resting expenditure of 1,400 kcal/day would get about 397 kcal, versus 567 kcal at 2,000 kcal/day. Neither is a direct measurement.

Do you burn fat while sleeping?

Your body uses stored fuels during sleep, but burning calories overnight is not the same as losing body fat overall. The experiments discussed above show why total energy intake and expenditure matter more than the isolated overnight number.

Do you burn more calories sleeping or lying awake?

Generally, lying awake uses more energy than sleeping under comparable resting conditions. As the Jung and Markwald experiments illustrate, that does not make sleep restriction a useful weight-loss strategy: extra eating can outweigh extra expenditure.

Conclusion

How many calories do you burn sleeping? Roughly 50 per hour is a useful reference, but your resting metabolism and hours asleep make the individual estimate more meaningful than the average. The key is treating that number as part of your daily expenditure—not bonus calories or a reason to sleep less.

For a clearer picture of the body behind those calculations, get a BodySpec DEXA scan to measure fat mass and lean tissue. It offers useful body composition data without pretending to measure an exact overnight calorie burn.