What are calories?
Put simply, calories are a measure of energy. Traditionally, it was a fairly common unit of energy, but nowadays it’s been relegated to describe almost solely nutrition and the energy content in food. The definition of a calorie is the energy required to raise the temperature of 1 gram of water by 1C. In modern times the definition of a calorie has been tuned and improved to a more reliable and repeatable one until we have arrived at the current: 1 calorie is equivalent to 4.18 joules.
In nutrition, we actually deal with kilocalories (kcal), where 1 kcal is equal to a thousand “small” calories. This kilocalorie is often called large calorie, Cal or Calorie (with capital ‘C’). As you imagine, 1 kcal = 4.18 kJ. In this article, we use the term “calories” to describe kilocalories for simplicity.
When you mention calories, people immediately think about nutrition, weight loss, and even health problems associated with being overweight, such as heart disease. This is because body fat and calories are very closely related. Body fat is the way our body stores energy for times of necessity, that is, body fat is how we store those extra calories that we ate but never burned. Fat is not necessarily a bad thing, as we explained in our healthy body fat calculator
There is a simple way to calculate calories from fat, which is based on the energy density of body fat. Each kilogram of body fat stores about 7700 kcal. This equivalence is what allows the burned calories calculator to predict the weight loss derived from a certain exercise. However, this is just an oversimplification since “calories in vs calories out” is not the whole story when it comes to weight loss. We will go a bit more into details in a later section, for now, let’s focus on the calculator.
How to calculate calories burned?
Since calories are, effectively, energy, any time energy is used or transformed in our body, we consume calories. This includes those times in which we are apparently doing “nothing” since, fortunately for us, our body is still functioning and consuming energy. The energy is consumed in activities such as pumping blood through our system, processing food in our digestive system and even thinking (the brain burns about 20% of our daily calories). But when we talk about consuming calories we tend to think more about the conscious act of exercising and expending extra energy compared to the normal or basal metabolic levels.
As you may have guessed, every exercise needs a different amount of energy. The number of calories burned walking is smaller than running or cycling. This energy expenditure is typically expressed in
MET – the Metabolic Equivalent of a Task. This measure tells you how many calories you burn per hour of activity and per one kilogram of body weight.
The MET value of an exercise is higher the more energy an activity requires. You can check that by looking at the different MET values for the exercises we have included in this calorie calculator. For example, sleeping has a value of 1 MET while running has a MET of 7.5, much higher.
What exactly is 1 MET, then? It is defined as the ratio of energy spent per unit time during a specific physical activity to a reference value of 3.5 ml O₂/(kg·min). While the MET values allow us to compare activities, they don’t measure energy directly. So you need another step to answer the question how many calories do I burn a day doing certain activity?. Answering that requires some recalculation and for you to convert milliliters of oxygen to calories before we arrive at the final formula:
calories = T * MET * 3.5 * W / (200 * 60)
where T is the duration of activity in seconds, and W is your weight in kilograms.
Our calorie burn calculator uses the formula above for the most accurate estimation of calories burned. If you want to run your calculations by hand, you can also use a simplified version of this equation:
calories = MET * T * W
This equation is based on the approximation that
1 MET = 1 kcal / (kg * h). It is not 100% correct since the real equivalence is
1 kcal/(kg * h) = 1.05 MET, as you can check from the initial formula. Nevertheless, the approximation simplifies calculations so much that a mere 5 percentage difference is an acceptable price to pay.
How many calories did I burn while cycling?
If you want to calculate the weight loss or calorie loss after a certain physical activity, make sure to follow the steps below. We have chosen to calculate the calories burned cycling, but you could calculate the calories burned walking following these same steps.
- Choose your activity and determine its MET value. For example, for cycling MET = 8.
- Input your weight into the calories burned calculator. Let’s assume you weigh 90 kg.
- Determine the duration of the activity. Let’s say you went for a whole day trip and were biking for 7 hours straight.
- Input all of these values into the calorie burned formula:
calories = T * 60 * MET * 3.5 * W / 200
calories = 7 * 60 * 8 * 3.5 * 90 / 200 = 6284 kcal
- Finally, divide this value by 7700 to obtain your weight loss:
6284/7700 = 0.82 kg
Congratulations! Your bike trip just helped you lose 0.65 kg. Now, it’s time to head to the BMI calculator and check where you place, just remember, it’s not a competition, just an indicator. You can also visit our BMR (Basal Metabolic Rate) calculator which will tell you how many calories your body requires for its basic existence. It will be a reasonable basis for constructing a new diet plan.
A deeper look at MET and the calorie calculator
Let’s now step back a little bit and look at how MET is calculated and what it really means. MET is a metric that assigns a single value to a certain activity, but, as anyone that has run or cycled frequently knows, the same exercise can vary in intensity significantly depending on the effort. There is a difference between going for a leisure ride with your kid and racing in a criterium, even if they both take the same time.
This is an effect that this calculator does not take into account: intensity. It is for this reason that the calories burned calculator needs to be understood as an approximation and not as a precise measurement. The MET we have encoded into this tool are just a guide based on averages and typical values for a typical person.
However, one can correct for this issue by simply customizing the MET value directly. We do not recommend doing this unless you know what you are doing or you are using a comprehensive database of MET values. The important thing to remember is that the MET values are not the be-all-and-end-all and should be taken with a pinch of salt. They, however, help you compare easily the calorie consumption expected from different exercises and activities. Simply choose I want to compare two activities option.