When discussing fitness, a major focus is often on the number of calories you eat and burn during exercise, especially when it comes to weight loss or weight gain. But did you know you're still burning calories even at rest? Even though exercising is important and has many health benefits, it only makes up a small percentage of the calories you burn throughout the day. In fact, most of the calories you burn go toward involuntary activities and everyday tasks like cooking and cleaning. 

There are many factors that determine how many calories you burn at rest versus during a workout, so we spoke to experts to get a clearer explanation. Read on to find out how many calories you burn daily and why it's helpful to know these details.

What determines how many calories you burn daily?

As you can imagine, the number of calories burned varies per person. Your total daily energy expenditure is the number of calories you burn in a day, including exercise. In order to get this figure, you first need to find out a few other calculations.

Basal metabolic rate

One of these key figures is your basal metabolic rate, which is the minimum number of calories your body needs to burn to maintain basic functions such as heart rate, breathing and digestion. "The number of calories your body burns while you're at rest is determined by your BMR," said Dr. Brittany Robles, an OB-GYN physician and a National Academy of Sports Medicine certified personal trainer. Things that affect your BMR include your age, weight, muscle mass and activity level. Your BMR accounts for about 60 to 75% of your daily energy expenditure. 

A helpful way to determine an estimate of what your BMR is, is by using the popular Harris-Benedict Equation. This formula takes into account your weight, height, age and gender. 

BMR calculations based on men and women:

Men: BMR = 66.5 + (13.75 * weight in kilograms) + (5.003 * height in centimeters) - (6.75 * age)

Women: BMR = 655.1 + (9.563 * weight in kg) + (1.850 * height in cm) - (4.676 * age)

Knowing your BMR can be helpful if one of your goals is to lose weight, but Robles says to keep in mind that this method is only an estimate. "The most accurate way to measure your BMR is through indirect calorimetry, which involves measuring your oxygen consumption and carbon dioxide production," she said. Generally, it's not necessary to go this far to measure your BMR since it's expensive, mainly used in research settings and isn't practical for everyday use.

Once you have an estimate of your BMR, you can use it to find your TDEE. To figure this out, you need to multiply the BMR and your activity factor. There are different types of formulas you can find online, but the Harris-Benedict Equation is the most popular and uses a rubric for activity factors that range from sedentary, moderate to strenuous. The rubric used is: 1.2 (for sedentary), 1.5 (for moderate) and 1.7 (for strenuous) and 1.9 (for very active individuals). 

Other factors that influence calories burned

Besides BMR, your resting metabolic rate, the thermic effect of food, non-exercise activity thermogenesis and exercise-related activity thermogenesis also play an important role. 

RMR: RMR and BMR tend to be used interchangeably because both make up the basis for how many calories you burn when you're not exercising. The difference is your RMR looks at the number of calories you burn when you're at rest, including regular activities like eating, while BMR only looks at the number of calories you burn for vital functions like breathing. To find out your RMR, you use the same BMR formula to get a result. 

TEF: The thermic effect of food is the number of calories your body burns in order to digest and absorb food. The TEF accounts for 10% of your daily energy expenditure. To find this number, calculate: BMR X 0.1= TEF.

NEAT: Non-exercise activity thermogenesis is the number of calories your body burns through activities that are not exercise, such as fidgeting, walking or doing other everyday tasks. It makes up about 15% of a sedentary person's total daily energy expenditure and up to 50% or more for highly active people. Your occupation heavily influences your NEAT. Hence, why a construction worker or someone who works on their feet all day will have a higher NEAT number than someone who works at a desk all day. 

In order to find out your NEAT number, you first need to know your total daily energy expenditure figure. Once you determine the figure that fits your lifestyle best, you'll be able to get your NEAT number.

The formula used to calculate NEAT is: TDEE - (BMR + TEF) = NEAT

EAT: Finally, EAT refers to intentional exercise and accounts for an estimated 15 to 30% of your total energy expenditure. Therefore exercise doesn't make up for much of your overall calories burned daily. 

"All of these factors play a role in how many calories you burn in a day," said Robles. "RMR and BMR make up the basis for how many calories you burn at rest, and TEF and NEAT add to this total by representing the number of calories you burn through activity."

Your body composition also affects calories burned

Now that you know about the different ways our bodies burn calories, it's important to understand how your lifestyle habits can influence this too. Matt Scarfo, a National Academy of Sports Medicine certified personal trainer, told CNET, "People with larger bodies burn more calories than those with smaller bodies because they need to keep their blood flowing, their muscles oxygenated and their cells operating." Additionally, if your body composition changes, the number of calories you burn at rest will change.

"Individuals with higher muscle mass tend to burn more calories at rest than those with less, since muscles require a lot of energy," explained Scarfo. Hormone cycles can also affect your energy needs, which is why some women get hungry during the high hormone phase of their cycle, leading up to their period. 

Then there are the changes that come with aging. "As you age you will often lose muscle mass, which leads to a slower metabolism," said Rachel Macpherson, an American Council on Exercise certified personal trainer and certified nutrition specialist. "Menopause and reduced testosterone can cause metabolic slow down as you age too," she added.

Therefore if you're trying to lose weight, gain weight or maintain your weight, knowing an estimate on how many calories you burn regularly can give you a better guideline on how many calories you should be intaking a day. "If you want to lose weight, you can decrease your calorie intake from your total daily energy expenditure, but only a small one so as not to slow your metabolism too much," explained Macpherson. Likewise, if you want to gain muscle or weight, you will need to eat more than you burn. 

Bottom line

It's important to remember that most of these calculations that determine how many calories you burn while exercising or at rest are simply estimates. They can help serve as a guide to help you better understand the different ways your body burns calories, but they're not definitive. If you're looking to lose weight, gain weight or simply maintain your weight, it's best to receive advice from a certified dietitian nutritionist. 

The information contained in this article is for educational and informational purposes only and is not intended as health or medical advice. Always consult a physician or other qualified health provider regarding any questions you may have about a medical condition or health objectives.