Calculator FAQ

In order to help you define your calorie needs, we have set up a calculator. Here we answer the most common questions.

  • Why do I need to calculate my calorie needs?

Calculating your needs allows you to have an estimation of the energy that your body uses to function properly. Why does that matter? Because your body doesn't function like your neighbors', colleague's, friends' or even family's. Your needs are based on your gender, age, weight, activity level and goal. This is not something that you can just copy on someone else! 

Finding the amount of calories that your body needs will therefore help you to build your diet accordingly, and hence efficiently achieve your goal, whatever it is.

  • How are my calorie needs calculated?

Several steps are needed to calculate your calorie needs:

1st step, we determine your basal metabolic rate (BMR)

2nd, we multiply it by your activity factor

3rd, we adapt the result to your goal: maintain/ lose/ gain weight

Now your understand why we made it super easy for you! You just have to enter a few data about you and you get your results in 1 clic!

  • What is a Basal Metabolic Rate? How is it calculated?

The Basal Metabolic Rate (BMR) is the amount of calories your body spends when you are doing absolutely nothing - lying in a bed the whole day. It just energy needed for your organs to work and your body temperature to be maintained.

Science and clinical studies have been working on finding the best way to predict someone's calorie needs as accurately as possible. Throughout the years, several equations have been established to predict the BMR, based on data from patients in clinical studies and mathematical models.

The first one, called Harris-Benedict, dates back to 1919 - and believe it or not, its revised version is still in use today .  Then, the equations the most used by the online calculator nowadays, are from Schofield and Mifflin St Jeor2, introduced respectively in 1985 and 1990.

The NXT Level team of experts has gone through several scientific publications, and has decided to use the most modern equation to date: the Oxford equation introduced in 2005. This equation is more representative to the modern population and takes into account several ethnicity. Furthermore, it presents a good accuracy1.

The parameters needed by this equation to calculate your BMR are you gender, age and weight.

  • What is the activity factor? How do I identify my activity level?

The more you exercise, the more energy your body will need. In order, to quantify your amount of exercise and add it as a factor to calculate your needs, several cases have been defined:


Lightly active

Moderately active

Very active

Extra active

  • I see many calculators on line using the height as a parameter to calculate the calorie needs. Why your calculator doesn't use this parameter?

As mentioned before, a lot of on line calculators are based on the Mifflin-St Jeor equations, that do take into account the height (on the top of the age, weight and sex). We have decided to use a more recent system of equations, Oxford. The scientists who have set up these equations have chosen to do not take the height as a parameter because when incorporated to the calculations, it didn't lead to any significant changes of the result.

  • If I am pregnant, breastfeeding, under 18 or have any specific health condition, can I use the calculator?

And the answer is no. If you are in any of the situations above mentioned, we highly recommend that you refer to a general practitioner or doctor for nutritional advice.


If you want to know more about calories, their use by the body, and further topics linked to weight loss, feel free to check our nutrition blog.


1. Basal metabolic rate studies in humans: measurement and development of new equations.

2. A new predictive equation for resting energy expenditure in healthy individuals.