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Calculate Daily Calorie Intake

By Alan Frost, updated November, 2013

man rides mountain-bike Knowing your required daily calorie intake is the first step towards maintaining, losing, or gaining weight – all depending on your specific fitness goal. Calorie calculations are always going to be an estimate, because we are all different. However, having a good estimate is necessary so that you can then refine the figure with trial and error.

Below, I will walk you through the calculations. However, you can always just simply use our Daily Calorie Calculator.

So what does your daily calorie intake consist of? Well, put simply it is the sum of two factors:

  1. The calories you burn at rest (i.e. just to stay alive). This is also called your basal metabolic rate or BMR.
  2. The calories you burn from being active.

Calculating BMR

Online, you can find a bunch of BMR calculators that use different variables. The worst of these do not take body composition into account. The problem with BMR is that it is heavily influenced by your body fat percentage. E.g. someone who weighs 200 pounds with a body fat percentage of 20% will have a far lower BMR than say a 200 pound bodybuilder with an 8% body fat percentage.

This is why many formulas do not give you results that you can trust. Even better formulas do not give results that are entirely precise, because they rely on a series of approximations (for instance, there are significant individual differences on how we metabolize energy). However, they will provide a much better starting point. If you do not want to go through the math, here is our own BMR Calculator.

All the methods described below therefore require that you know your lean body weight. For that you need your body fat percentage. There are many ways to do this with varying degrees of accuracy. One of the cheapest and best is to buy a set of body fat calipers for a few dollars. On our Body Fat Calculator page, you can find two calculators, one which uses tape measurements of various body parts and the other which uses measurements based on body fat calipers. You can also find a set of images which you can use to make a visual comparison to estimate your body fat.

So, if you weigh 200 lbs and have a body fat percentage of 20%, your lean body weight is 160 lbs.

Below, we will calculate BMR using the Katch-McArdle Formula, which relies exclusively on lean body weight (since this is the main determinant of metabolic activity).

BMR: (21.6 x lean body weight in kg) + 370

For conversion purposes:
body weight in kg = body weight in pounds divided by 2.2

So, our 200 lbs man (or woman) with a 20% body fat and hence 160lbs of lean body weight would have a BMR of:

(21.6 x 73kg) + 370= 1947 calories per day

Adding calories from being active

It is extremely hard to precisely measure your daily calories from being active. It's not just the sports and the cardios, it is also the difference between lying down and sitting up, walking slowly or briskly, being out and about vs staying at home, etc. The best we can do is get an approximation.

To do this, I will use ISSA's modifiers for "Average Daily Activity Levels" (Hatfield, 2004):

1.30: Very light activity. Includes sitting, talking, and performing minor activities with only a little walking around.
1.55: Light activity. Typing, shop work, some walking during the day.
1.65: Moderate activity. Jogging, gardening type work, and activities like biking, tennis, dancing, or weight lifting for 1 to 2 hours per day.
1.80: Heavy activity: Heavy manual labor with activities like intensive sports (e.g. soccer, basketball, bodybuilding) for 2 to 4 hours per day.
2.00: Very heavy. 8 or more hours of moderate and heavy activity, as well as 2-4 hours intensive daily training.

Putting it all together

To estimate your required daily calorie intake, simply multiply the figure for your BMR by your activity level multiplier.

In our previous example, if our 200lbs man or woman was moderately active, his/her daily calorie expenditure would be: 1947 x 1.65= 3213 calories.

In other words, this individual would have an estimated daily calorie intake requirement of 3213 in order to break even.

Remember that this is just an estimate, which you can refine over time through trial and error. With this number, you can calculate the amount of protein, carbohydrates, and fats that you require each day. For this please see Calculating your Macronutrient Ratio.

References:

Hatfield FC (2004), Fitness The Complete Guide edition 8.6.6, International Sports Science Association's Certified Fitness Trainer Program



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