When you think about the number of calories you burn throughout the day, you probably don’t give much thought to what happens overnight. After all, how many calories could you possibly burn while sleeping? It turns out you might be surprised.

It requires a certain amount of energy to keep your body alive and breathing. Because of that, your body is burning calories even when you aren’t doing anything. While there’s no way to definitively know how many calories you burn per night, there’s a calculation you can use to estimate fairly closely.

How Many Calories Do You Burn While You Sleep?

According to Harvard University, most people can expect to burn roughly 40-55 calories per hour while sleeping. Using that number, you might think it would be pretty easy to figure out how many calories you burn in a night. But it’s a little more complicated than that. The number of calories each person burns while sleeping depends on a formula based on your gender, weight, height, and age. Don’t worry — it’s an easy calculation to do at home. And once you do, you’ll be able to estimate your nightly calorie burn easily.

Calculating How Many Calories You Burn While Sleeping

The number of calories you burn while sleeping is determined by your basal metabolic rate (BMR). Your BMR is the baseline number of calories your body requires to maintain bodily functions like breathing, keeping your heart beating, and regulating your body temperature. For most of us, our BMR accounts for roughly two-thirds of the calories we burn each day. 

It’s important to note that not everyone has the same BMR. Your gender, weight, and age all impact your BMR. A laboratory test can help you to figure out your exact BMR. But since most people aren’t likely to go through the trouble, there’s a formula you can use at home to help you estimate:

Women: 

BMR = (10 x weight in kilograms) + (6.25 x height in centimeters) – (5 x age in years) – 161

Men: 

BMR = (10 x weight in kilograms) + (6.25 x height in centimeters) – (5 x age in years) + 5

Once you estimate your BMR, you can easily determine how many calories you likely burn while sleeping. First, since your body burns fewer calories while sleeping than it does while you’re awake, multiple your BMR by 0.85 to determine your sleeping BMR. Then, multiply your sleeping BMR by the number of hours you sleep. So if you sleep for eight hours per day, the formula to determine the number of calories you burn while sleeping would be:

Calories Burned = BMR x 0.85 x 8 hours

Other Factors That Impact The Amount Of Calories Burned By Sleeping

It’s not just your BMR that determines the number of calories you burn while you sleep. Your daily habits can also play an important role. Let’s talk about some specific factors that impact the number of calories you burn overnight.

Your Eating Habits

It probably comes as no surprise that your nutrition can impact the number of calories you burn while sleeping. First, maintaining a healthy diet can boost your metabolism, including overnight. The time of day you eat also impacts your calorie burn, but not in the way you might think. Many argue that eating late at night slows your metabolism and causes you to gain weight. In reality, it’s not eating late at night that has the greatest impact. Instead, people who eat late at night tend to choose unhealthy snacks, which has a bigger impact on your calorie burn.

How Active You Are

Studies have shown that regular exercise can improve your sleep and increase the number of calories you burn while asleep. This is especially true of activities like weightlifting that increase your muscle mass. These workouts tend to increase your metabolism long after you finish your workout, meaning you burn more calories overnight.

The Amount Of Sleep You Get

You might think that the less sleep you get, the more calories you burn in a day. After all, you burn fewer calories per hour asleep than awake. In reality, other negative health effects of sleep deprivation overcompensate for the potential extra calorie burn. A chronic lack of sleep can lead to weight gain. 

Sleep Stage

You don’t burn the same number of calories per hour the entire time you’re sleeping. Instead, you burn a different amount of calories during different sleep stages. You burn the most calories during REM sleep — your heart rate increases during this stage, requiring your body to work a bit harder to function. The calorie burn during this sleep stage more closely resembles your BMR when you’re awake. In your deepest sleep stage, your heart rate slows, and you burn fewer calories. 

Interruptions to your normal sleep cycle that reduce your REM sleep could also reduce the number of calories you burn per night.

Sleep Temperature

Sleeping in a cooler environment can help to increase your metabolism, and therefore increase the number of calories you burn hourly. Ways to reduce your body temperature include reducing the room temperature in your bedroom and sleeping in lighter clothing.

Final Thoughts

It turns out that we actually do burn calories overnight. By taking into account factors like your gender, weight, height, age, and number of hours of sleep you get, you can try to calculate your nightly calorie burn. There are plenty of other factors that can impact the number of calories you burn while sleeping, including your eating and exercise habits. Just remember — a healthy diet, regular exercise, and a regular sleep schedule are best for both your calorie burn and your overall health.