Whether you’re trying to lose weight, build muscle or fuel sporting performance, getting your calorie intake is right is crucial to progress. A number of factors will influence how many calories you expend, including your body weight, height, age and physical activity level.
In order to calculate your daily calorie requirements, you should calculate how many calories your body expends when doing nothing. This is your resting basal metabolic rate (BMR). Your BMR should then be multiplied by an activity factor which will depend of your lifestyle and training demands. The final factor when calculating your total energy expenditure is the thermic effect of food, which is the energy needed to digest, absorb and metabolise your food.
Let’s dive into each of these components and how they can help you figure out how many calories you burn in a day.
- Calculating your BMR.
- Calculating your activity level.
- Thermic effects of food.
- How many calories do you burn a day?
- How many calories do you burn from exercise?
- How many calories do you burn from household tasks.
Step 1: Calculate Your BMR
Your basal metabolic rate is the energy your body expends to keep your body and vital organs functioning properly.1 For most people it accounts for largest majority of total daily energy expenditure and ranges form 40-70% of TDEE depending on age and lifestyle.1
The easiest (and cheapest) way to calculate your BMR is to use an equation. How accurate each equation is for you specifically will depend on how closely you match the population that the equation was tested and validated in.2 For example, in highly active females, the Cunningham equation may be the most accurate but for highly active males, the Harris-Benedict equation may be more suitable.2 Certain equations (e.g. Cunningham) also require an estimation of your lean body mass.
It is important to remember that calculating your calorie requirements is not an exact science and there is an element of trial and error.
See below for an example of Mifflin. St. Jeor equation which has been shown to be one of the most accurate equations without the need for a lean body mass measurement3.
10 * weight (kg) + 6.26* height (cm) – 5* age (years) + 5
Looking for more info on BMR? Read this next.
Step 2: Calculate Your Activity Level
In order to calculate your total daily energy requirements, your BMR should be multiplied by a physical activity factor. This is the element of energy expenditure that will vary most between individuals and will range from 1.2 to 2+ depending on your lifestyle and training demands1.
Here’s a table to give you an indication on which physical activity factor to choose4,5:
The thermic effect of food is another thing to consider when you account for energy expenditure. This is the energy it takes your body to digest, absorb and metabolise your food. Whilst certain foods have a greater effect on energy expenditure than others, it’s estimated the thermic effect of food accounts for 10% of total energy expenditure1. Females: Sedentary (kcals) Moderately Active (kcals) Highly active (kcals)
Physical Activity Factor
Typical office work and occasionally active
Some manual work and/or regular exercise
Large amount of manual work and/or exercise
Step 3: Thermic Effect of Food
How Many Calories Do You Burn A Day?
Body Weight (kg)
The thermic effect of food is another thing to consider when you account for energy expenditure.
This is the energy it takes your body to digest, absorb and metabolise your food. Whilst certain foods have a greater effect on energy expenditure than others, it’s estimated the thermic effect of food accounts for 10% of total energy expenditure1.
|Highly active (kcals)|
How Many Calories Do You Burn From Exercise?
Number of calories burned per 20 minutes of exercise in individuals with different body weights:
|cycling stationary, light||3.5||61||74||86||98||110|
|cycling stationary, moderate||6.8||119||143||167||190||214|
|cycling stationary, vigorous||8.8||154||185||216||246||277|
|running 6mph (10min/mile)||9.8||172||206||240||274||309|
|running 7mph (8.5min/mile)||11.5||201||242||282||322||362|
|running, 8mph (7min/mile)||11.8||207||248||289||330||372|
How Many Calories Do You Burn From Household Activities?
Number of calories burned per 20 minutes of activity in individuals with different body weights:
|Sitting in meetings||1.3||23||27||32||36||41|
Take Home Message
Your energy expenditure is made up of three main parts – your basal metabolic rate, physical activity level and the thermic effect of food. Without using expensive laboratory kit, calculating the exact number of calories expended can be difficult to get right with a number of factors affecting the accuracy of an estimation.
Using the equations included will give you a rough idea of how many calories you require with physical activity being the biggest variable between individuals.