Boost Your Nutrition

with National Academy of Sports Medicine

NASM Nutrition Series
Understanding Food Labels
& Portion Sizes

NASM's Calorie Calculator

Calorie calculators, like the one below, are a great resource for quickly determining a weight loss plan based on calorie expenditure, activity levels, and overall goals.

Weight loss calculators work by measuring: Basal Metabolic Rate (often called Resting Metabolic Rate), Total Daily Energy Expenditure (TDEE), a goal weight by a desired date, and your current intake ratio of carbs, fats, and protein.

If you want to learn how to manually calculate calories, read the steps below. You can also check out our online nutrition courses, Weight Loss Specialist Program, and even our BMI Calculator (if you want to use another great tool).

a woman eating a healthy salad after calculating her weight loss goals
 

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How to Calculate Calories in 4 Steps

Step 1: Determine BMR

Determine you (or your client’s) basal metabolic rate (BMR) by using the Mifflin-St Jeor equation:

  • Men: (10 × weight in kg) + (6.25 × height in cm) - (5 × age in years) + 5
  • Women: (10 × weight in kg) + (6.25 × height in cm) - (5 × age in years) - 161


Step 2: Measure Total Daily Energy Expenditure

Measure Total Daily Energy Expenditure (TDEE) by multiplying your BMR by the Katch-McArdle multipliers:

  • Sedentary (little to no exercise + work a desk job) = 1.2
  • Lightly Active (light exercise 1-3 days / week) = 1.375
  • Moderately Active (moderate exercise 3-5 days / week) = 1.55
  • Very Active (heavy exercise 6-7 days / week) = 1.725
  • Extremely Active (strenuous training 2x / day) = 1.9


Step 3: Determine Goal Weight and Desired Weight Loss Date

  1. Subtract goal weight from current weight
  2. For example: 150lbs -20lbs = 130lbs
  3. Take lbs of weight loss needed and divide by 2, 1.5, 1. This will give you an idea of how many weeks it would take to reach your goal weight if you lost 2lbs/week, 1.5lbs/week, or 1lb/week .

For example: 20/2 = 10 weeks to reach goal weight, 20/1.5 = 13 weeks to reach goal weight, or 20/1 = 20 weeks to reach goal weight.



Step 4: Calculate Macronutrient Ratios


This is the last step of calculating calories, and it's one that's absolutely essential for getting accurate weight loss results.


First: Calculate Daily Protein Needs

Did you know that protein is a huge catalyst for weight loss and hunger satiation? Let's compare and contrasts sedentary versus moderately active individuals and their protein requirements.

  • For sedentary/lightly active individuals: 1-1.2g/kg/day
  • For moderately active - extremely active: 1.4-2.2g/kg/day

Convert body weight in pounds to kg’s (round to the nearest 10th)

  • 150lbs / 2.2 = 68.2kg

Multiply weight in kilograms by range that best fits your activity levels.

  • 68.2kg(1g) = 68g
  • 68.2kg(1.2) = 82g


Second: Calculate Daily Fat Needs

To prevent any fatty acid deficiencies it is recommended to consume at minimum 1g/kg of fat per day. The Dietary Guidelines for Americans also recommends fat should make up 20-35% of one’s total daily calories. Using both of these references you can calculate your daily fat needs:

To calculate fat:

  • Convert body weight in pounds to kg’s (round to the nearest 10th)
  • 150lbs / 2.2 = 68.2kg
  • Multiply weight in kilograms by 1
  • 68g of fat needed per day

    • See this blog on How Much Fat Per Day for Weight Loss to learn more.



Third: Calculate Daily Carbohydrate needs

The Dietary Guidelines for Americans recommends that carbohydrates should make up 45-65% of one’s daily calories.

Step 1: Calculating grams of carbohydrates. Multiply daily calorie requirements by 0.45 & 0.65 to obtain calories from carbohydrates.

  • 0.45(2000) = 900 calories
  • 0.65(2000) = 1300 calories

Step 2: Divide answers in step 1 by 4 since there are 4 calories per 1 gram of carbohydrate

How Many Calories Do You Need a Day to Lose Weight?

For healthy, sustainable weight loss, it is generally not advisable to lose more than 2 pounds of fat per week. That would equate to a calorie deficit of 1,000 calories per day. More often than not, when weight loss exceeds 2lbs in a week, the majority of that is water loss. So keeping that in mind, the goal is to lose 1-2lbs per week.

For sedentary individuals, it would be recommended to set a goal of losing 1lb per week, which would equate to a calorie deficit of 500 calories/day.

For more active individuals, daily calorie requirements are higher in order to account for exercise and active lifestyles. Taking this into consideration, it is more feasible to cut back on food since daily caloric requirements for maintaining weight are much higher. Therefore, creating a calorie deficit of 500-1,000 calories per day can lead to a max weight loss rate of 2lbs/week.

Remember, combining exercise with a small calorie deficit is the best intervention to maximize weight loss! Additionally, consuming a high protein diet (or sticking to the higher ranges based on your activity level) will help maintain and preserve muscle mass while losing fat.

a man preparing vegetables in a kitchen after calculating calories
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