How to calculate your 'Macros'

I've previously discussed the importance of eating enough calories to improve your metabolism. If you missed that you can read it here. But it is also important to look at your macronutrient intake. 

Have you ever wondered what “IIFYM’ stands for or what ‘Macros” mean? 

Macronutrients are Protein, Fat and Carbohydrates. Your body needs a certain amount of each macronutrient to perform optimally. 


Protein is the building block of the body. It makes up a part of nearly every cell in the body and is vital for muscle repair and growth and is also a source of energy. Sources include meat, poultry, eggs, lentils, beans. Some people struggle to reach their protein goals in a day and this is where the need for supplements such as protein shakes and bars. It is ideal to get your protein intake from natural sources.


Fat is an important part of the diet and for many years was seen as the enemy. I think general opinions have changed and people now realise that ‘low fat’ does not necessarily mean healthy. There are different types of fat. Polyunsaturated, Monounsaturated, Saturated (which are all necessary in the diet in different proportions) but the one you want to avoid is Trans Fat. Trans Fat is created from an industrial process where hydrogen is added to vegetable oil to make it solid at room temperature. It prolongs the shelf life of the product containing it. It is usually not labelled as trans fat. 


Carbohydrates or ‘carbs’ are the main fuel source for the body. When carbs are digested, they are converted to glycogen which is stored in the muscles and liver for energy. Unused glycogen is converted to body fat. For this reason, many people avoid carbs altogether and rely on protein and fat as fuel. It is a much better practice to eat carbs, which will increase energy and the ability to train, resulting in more muscle and in turn, a higher BMR.

Calculating your personal macronutrient requirements

There are many calculators online that will give you an estimate of your ‘macros’ using your height, weight and age but these are all quite variable. Especially as you also have to estimate activity level. I tested several different methods and calculations on myself and then developed a calculator in excel using the method I found worked for me. Ideally you should work with a PT or nutritionist since it is so individual and variable. 

One of the most popular websites would be's calculator.

If you would like me to send you the excel calculator I developed you can get a copy here for less than the price of a pizza. (My maths degree is finally paying off!) 

Tips for tracking your macros

  • Go to on a desktop browser to set up your account

  • Don’t use the recommended guidelines but select the ‘custom’ option

  • Don’t enter a goal weight 

  • For the calorie requirement, use the number calculated from the calculator/website

  • For the protein, fat and carbs you should change the percentages until it hits as close as possible to the grams calculated

  • In the settings, set the meals into ‘Meal 1’, ‘Meal 2’ etc for as many times as you plan to eat a day

  • Set the default macros to be shown as just the ‘Protein’, ‘Fat’ and ‘Carbohydrates’

  • Plan a day’s food so that the total macros are hit - i.e. the amount of protein, fat and carbs match your goals as close as possible. As a rule of thumb, +/- 10g of each macro is ok

  • Use some staple adjustable items in your day so you can change the amount as necessary for the different macro requirements e.g. Oats and Protein Powder - you can increase or decrease the amount of oats or powder to increase or decrease the carbs or protein consumed

  • Once you have planned a days food is useful to aim to eat the same food for a few days

  • If you have something outside of your plan, track it as soon as possible and adjust the rest of the days food to make it fit

Eating for exercise/Carb Loading/Glycemic Index

These topics are more advanced and I would guide people on an individual basis. Initially you should be able to plan and track your food using your macronutrients as a guideline.

I hope this basic explanation is helpful to some people as I get so many emails requesting help with macros.  I won't be able to answer individual emails regarding macros. I will be giving individual advice through my online coaching program. I am trying to find time to launch it but the one-on-one training has my days very busy. To register your interest for online coaching or personal training, click here.

Siobhan x