Most people burn roughly 50 calories per hour while sleeping, which adds up to about 400 calories over an eight-hour night. Your actual number depends on your body size, age, sex, and muscle mass, and it can vary by 20% or more from that average. Here’s how to estimate your personal number and what influences it.
How to Calculate Your Sleep Calorie Burn
The most widely used method starts with the Harris-Benedict equation, which estimates your basal metabolic rate (BMR), the energy your body uses just to keep itself running while awake. The formulas look like this:
- Male: BMR = 66.5 + (13.8 × weight in kg) + (5 × height in cm) − (6.8 × age in years)
- Female: BMR = 655 + (9.6 × weight in kg) + (1.8 × height in cm) − (4.7 × age in years)
That gives you a 24-hour number for waking rest. To convert it to a sleep estimate, divide by 24 to get an hourly rate, then multiply by 0.85. That 15% reduction accounts for the fact that your metabolism slows down when you’re asleep. Multiply the result by the number of hours you sleep, and you have a reasonable estimate for the night.
For a quick example: a 35-year-old man who weighs 180 pounds (82 kg) and stands 5’10” (178 cm) has a BMR of about 1,840 calories per day. His hourly awake rate is roughly 77 calories, and his hourly sleep rate is about 65 calories. Over eight hours of sleep, that’s around 520 calories. A 35-year-old woman who weighs 140 pounds (64 kg) and stands 5’5″ (165 cm) would come in closer to 440 calories for the same eight hours.
What Your Body Is Doing While You Sleep
Sleep looks passive, but your body is running a long checklist of maintenance tasks. Your brain is consolidating memories and clearing waste products. Your cells are repairing tissue. Your endocrine system is releasing growth hormone. Your heart continues pumping, your lungs keep expanding, and your core temperature is being carefully regulated. All of this requires energy, which is why you still burn a meaningful number of calories even though you’re lying perfectly still.
Your metabolic rate isn’t constant throughout the night, either. It tends to dip during the deeper stages of sleep earlier in the night and rises slightly during REM sleep, when brain activity increases. The overall average still falls below your waking resting rate, but it’s not as low as you might expect.
Why Body Composition Matters More Than Weight
Two people who weigh the same can burn noticeably different amounts of calories during sleep. The reason is muscle. Muscle tissue is more metabolically active than fat tissue, meaning it demands more energy even at rest. Someone with a higher proportion of lean muscle will have a higher basal metabolic rate and, by extension, burn more calories while sleeping.
This is one reason resistance training shows up in metabolism conversations so often. Building and maintaining muscle through strength exercises raises your baseline calorie burn around the clock, including overnight. On the flip side, diets high in added sugars and saturated fats can make it harder to maintain muscle mass over time, gradually lowering your resting metabolism.
Room Temperature and Brown Fat
The temperature of your bedroom can nudge your overnight calorie burn in either direction. A study from the National Institutes of Health had participants sleep in rooms set to different temperatures over several months. After a month of sleeping at 66°F (19°C), the subjects developed more brown fat, a type of fat that burns calories to generate heat and maintain core body temperature. White fat, by contrast, mainly stores energy.
The metabolic shift from the extra brown fat wasn’t dramatic enough to cause weight loss on its own, but it did improve markers related to blood sugar regulation and diabetes risk. Interestingly, when the same participants later spent a month sleeping at 81°F (27°C), the brown fat gains reversed completely. They actually ended up with less brown fat than they started with. Keeping your room on the cooler side is a simple, low-effort way to support slightly higher overnight energy expenditure.
How Poor Sleep Disrupts Hunger and Metabolism
The calorie question cuts both ways. Sleeping burns calories, but not sleeping enough can cause you to take in far more than you save. Sleep deprivation throws off two key appetite hormones: leptin, which signals fullness, and ghrelin, which signals hunger. During normal sleep, leptin rises to suppress appetite during the overnight fast while ghrelin naturally tapers off in the second half of the night.
When sleep is cut short, this system goes haywire. In a controlled study comparing two nights of four hours in bed to two nights of ten hours, the short-sleep condition produced an 18% drop in leptin and a 28% spike in ghrelin. Participants reported 24% more hunger and 23% more overall appetite the next day. The ratio of ghrelin to leptin, essentially a hunger-to-fullness ratio, closely tracked how hungry people actually felt.
The metabolic damage goes beyond appetite. Sleep debt reduced glucose tolerance by more than 40% in one study, meaning the body became significantly worse at processing blood sugar. Evening cortisol levels also rose, and insulin sensitivity dropped. These changes followed a dose-response pattern: less sleep meant more disruption. In practical terms, chronically short sleep doesn’t just leave you tired. It actively pushes your body toward overeating and less efficient metabolism.
Does Eating Before Bed Change Overnight Burn?
Eating late at night appears to lower how many calories your body burns, though the research is still being refined. A 2022 study published in Cell Metabolism found that late eating decreased waking energy expenditure and lowered 24-hour core body temperature compared to eating earlier in the day. The thermic effect of food, the energy your body uses to digest a meal, tends to be lower in the evening than in the morning. This difference appears to be driven by your body’s internal circadian clock rather than just the act of eating itself.
The practical takeaway is straightforward: eating the same meal earlier in the day costs your body more energy to process than eating it right before bed. While the overnight difference for any single meal is modest, the pattern can add up over weeks and months.
A Quick Reference by Body Size
Since individual calculations can be tedious, here are rough estimates for eight hours of sleep based on common body weights. These assume an average height, age in the mid-30s, and moderate body composition:
- 125 lbs (57 kg): approximately 340–380 calories per night
- 155 lbs (70 kg): approximately 400–450 calories per night
- 185 lbs (84 kg): approximately 470–530 calories per night
- 215 lbs (98 kg): approximately 540–600 calories per night
These are ballpark figures. Your actual number will shift based on your muscle-to-fat ratio, age, and even how cool your bedroom is. But for most adults, a full night of sleep burns somewhere between 300 and 600 calories, a meaningful chunk of your daily energy budget that your body is putting to good use while you rest.