Calculate your calorie needs

If you want to know how many calories you should be consuming in a day then follow this calorie counting guide from nutritionist Nancy Clark, MS, RD.

Calculate your calorie needs

Nutrition today is evolving into nutrition by numbers. Nutrition facts printed on food labels give us accurate information on what we're eating, but we need to learn how to use that information on a personal level.

Many of us know about grams of protein, fat and carbohydrates, but do you know your daily budget for these nutrients? By reading this article you will be able to calculate your own personal nutritional needs for calories and grams of fat, protein and carbohydrates. Using this information, you'll be able to use to your advantage the nutrition facts on food packages and in restaurants.

Calorie count - how many calories do I need a day?

Knowing your calories is important information for both food label readers and calorie counters. After all, the only way to determine if one serving of breakfast cereal is too much or too little food is to determine how it relates to your whole day's calorie needs. 

How to work out your calorie needs:

1. Your weight lbs x 10 (kg x 22)

This estimates your Resting Metabolic Rate or RMR, the amount of fuel you burn simply doing nothing all day except breathing, pumping blood, growing hair, and existing. For example, if you weigh 140 pounds, your RMR is approximately 1,400 calories (140 pounds x 10 calories per pound).

2. Add half that number again

Add to your RMR about half of your RMR; this accounts for the calories you burn with moderate daily activity apart from your purposeful exercise. For example, a moderately active 140lb woman requires about 1,400 calories for her RMR plus 700 more calories (half of 1,400) for activities of daily living, which equals 2,100 calories per day. (N.B. You may need 30 to 70% of your RMR, depending if you are mostly inactive or very active during the day.)

3. Add calories for your purposeful exercise (approx. 100 calories per mile)

At health clubs, the exercise machines offer a reasonable estimate of how many calories you burn on the treadmill or cross trainer. Runners can estimate about 100 calories per mile (based on a 140lb person). In general, you can guess about 400 to 600 calories per hour of aerobic exercise. Hence, a 140lb person who does 45 minutes of aerobics might burn 300 calories per class, bringing her daily needs to 2,400 calories per day. 

4. To lose weight, subtract 20%

If you want to lose weight, subtract 20 per cent of calories: 2,400 - (20% x 2,400 = about 500 calories) = 1,900 calories for a reducing diet.

Divide your calories evenly throughout the day: 2,400 calories total = 800 calories for breakfast/snack, 800 for lunch/snack and 800 for dinner/snack. The reducing program offers 600-700-600 = 1,900 calories.

Using these numbers and the food label facts, you can compare your intake to your needs. For example, you can now understand why one serving of cereal for 100 calories leaves you hungry if you need to eat 600 to 800 calories!

Calculate your daily fat needs

For most active people approximately 25 per cent of their calories should come from fat. This invests in heart health, as well as allowing for more carbohydrates to fuel the muscles. If you have a family history of heart disease and your blood tests indicate your cholesterol is high (>200 dl, and a HDL <50), you might want to target a lower fat diet with 20% of the calories from fat.
Example: 25% of 2,400 calories = 600 calories of fat = 66 grams of fat per day (one gram fat has nine calories). If you've been avoiding foods with more than five grams of fat, think again. A low fat diet is very different from a no fat diet and allows for a little fat at each meal. Preferably, you'll choose a health-protective fat, such as the plant fats in olive oil, nuts, tofu, and the fish fats in salmon and swordfish. 

Calculate your protein needs

Protein needs shouldn't be based on a percentage of calories. That's because protein needs are based on your body weight, not on your calorie intake. The following example shows the problems associated with calculating protein on percentage of calories:


  • 30% x 1,000 calories = 330 protein calories = 82 grams of protein
  • 30% x 3,000 calories = 990 grams of protein = 250 grams of protein.

For most athletes, allow 0.5 to 0.75 grams protein per pound of (appropriate) body weight. This means, a 140 pound person needs about 70 to 105 grams of protein per day. By reading the label on the can of tuna, you can learn the whole can has 40 grams of protein and is a strong start to meeting your needs. Maybe you don't need that protein supplement after all!

Nancy Clark, MS, RD, nutritionist in the Boston area, teaches active people how to be successful with food. Her best-selling Sports Nutrition Guidebook as well as her Food Guide for Marathoners and Food Guide for New Runners offer more information to help you reach your goals. See

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