How to calculate calorie deficit?

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Are you looking to lose weight and shed some excess fat? If yes, then you’ll need to be in a calorie deficit. You may be wondering what a calorie deficit is, how to calculate It and how to ensure it’s healthy right? Well, don’t worry we cover everything you need to know in this post.

What is a calorie deficit?

Calories can be a difficult concept to grasp because it’s not a physical term, it is a unit of measurement. For instance, kilograms and grams are a unit of measurement for weight, and metres, kilometres, and miles are a unit of measurement for distance. Calories are a unit of measurement for energy. When you consume food and beverages, you will be eating calories, and in different terms, you will be eating an amount of energy to help you do your daily tasks, physical activity, and to support a variety of bodily functions not visible to the eye like brain functioning.

A calorie deficit is achieved when your calorie intakes are lower than your energy expenditure. Energy expenditure is the number of calories your body requires to maintain your current weight. So in order to achieve a calorie deficit, you will need to know how many calories your body needs to maintain your weight and then reduce them depending on how much weight you’re looking to lose. We will get into that in just a second don’t worry.   

How calorie deficit works?

A calorie deficit breaks down fat stores to release fatty acids so they can be used for energy. This is to obtain enough energy to fuel your daily errands, exercise, and so on.

How to calculate a calorie deficit?


The first step to calculating your calorie deficit is to calculate the maintenance calories. This can be done automatically with the help of our online calculator but you can also do it manually as shown below.

Calculating your maintenance calories:

We use the Harris-Benedict equation to calculate maintenance calories, which is very accurate and takes into account all aspects of your body composition. The breakdown of this equation is given below; however, keep in mind that it varies for men and women, so make sure to calculate your maintenance calories using the appropriate gender ratios. The first move is to assess your Basal Metabolic Rate (BMR). BMR is the term given to the number of calories that the body burns per day at rest, it is also referred to as metabolism.

MEN – (88.362 + (13.397 x body weight in KG) +4.799 x Height in CM) – (5.677 x age) = BMR

WOMEN – 447.593 + (9.247 x body weight in KG) + (3.098 x Height in CM) – (4.330 x age) = BMR

When doing these calculations, don’t forget about BODMAS! Calculate the brackets first, then add, and then subtract.

Just to help you understand the equation a little easier, we’ll do an example. Let’s calculate the BMR for a 1.65m tall lady who is 27 years old and weighs 62kg.

447.593 + (9.247 x 62) + (3.098 x 165) – (4.330 x 27)

447.593 + 573.314 + 511.17 – 116.91

BMR = 1,415.167

Once you’ve measured your BMR, you’ll need to multiply it by your activity level. Each activity level reflects how busy your lifestyle is. Simply determine which activity level best describes your lifestyle and multiply your BMR by the corresponding number.

Activity Levels

Sedentary – 1.2 (work at an office and do not exercise)

Light Activity – 1.375 (Either you work in an active occupation eg. Waitressing or you work in an office job but sometimes exercise)

Moderate Activity – 1.55 (You may work in a sedentary job but exercise very regularly or you may simply be working at a physically demanding job eg: Labourer)

Very active – 1.725 (You may exercise most days of the week and you may work in an active occupation)

Extra active – 1.9 (You exercise every day and you work in a physically demanding job)

To continue with our previous example, our calculations reveal that our hypothetical lady’s BMR is 1,415.167, and we’ll assume she’s moderately active. As 1.55 is the corresponding number beside the activity level, we’ll need to multiply 1,415.167 by 1.55.

1,415.167 x 1.55 = 2,194 (rounded up)

So, If our lady consumed 2,194 calories per day, she will maintain her current weight. It may still fluctuate due to hormones and water retention, but she will roughly stay the same weight.

Calculating the calorie deficit:

Before calculating the calorie deficit, set a weight goal and a time frame for yourself. However, you must be cautious when setting your goals because the lower the calorie deficit, the more likely you will gain the weight back on

Furthermore, a significant calorie deficit may have harmful effects on your hormones since the body goes into starvation mode. This may also contribute to malnutrition if you don’t eat a well-balanced diet. If this is of your concern, you can take a look at our personalised diets, we can create a diet plan that’s tailored to your goals.

The greater the calorie deficit, the quicker you’ll lose weight, but the greater the risk of gaining it back. So, how much of a calorie deficit is considered safe? A calorie deficit that leads to no more than 1-1.2 pounds weight loss per week is considered healthy.

How to calculate the deficit?

Over the years scientists have cracked the code. To lose 1lb of weight in 1 week, you will need to eat 500 calories less than your maintenance calories. It’s important to understand that to lose weight, you need to be in a calorie deficit consistently. This means you must be eating 500 calories less every single day. You don’t lose weight from one day to another but rather over 3-7 days. Scientists have discovered that 1lb of fat is made from 3,500 excess calories. Therefore, being in a calorie deficit for 7 days means that you will be short of 3,500 calories by the end of the week. This will result in a weight loss of 1lb of fat (500 x 7= 3,500).

Is calorie deficit all that matters?

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A calorie deficit is the biggest driver of weight loss, you can lose weight without exercise by being in a calorie deficit but the best way to shape up and tone up your body is through exercise.

Also, the whole calorie equation can be affected by a variety of things like medical conditions like MS and an underactive thyroid, certain medicines can also cause weight gain and slow metabolism. So if you are suffering from any medical conditions or taking any medicines, make sure to read the potential side effects or ask your doctor if these can cause weight gain as there may be alternatives you can take.

In addition, muscle mass is also very important. Did you know that 1lb of muscle can burn an extra 60 calories per day? Therefore, your second priority should be lifting weights and maintaining muscle mass.

Why is calorie deficit not working?

As we’ve previously mentioned, losing weight occurs over 3-7 days when you remain within your deficit consistently. If you have a cheat day, this can ruin your calorie deficit and potentially take you over your maintenance calories. Watch the video below to understand how cheat days can ruin your dieting with just 1 day, and how to prevent it whilst still enjoy your cheat day.

When to stop the deficit?

A calorie deficit should not be disrupted from one day to the next, as this would only lead to weight gain. Your body won’t be able to manage it due to metabolic adaptations. Instead, devote your time to reverse dieting, which is a post-diet diet that allows you to increase your calorie intake without gaining weight.


A calorie deficit refers to eating fewer calories than what the body needs to maintain its current weight. The deficit can be achieved by either eating less food or by exercising to burn extra calories. By now you should know how to calculate your calorie deficit and how to lose 1lb of weight per week. We hope this information was helpful, let us know below in the comments.

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