How To Calculate Calories

Use some simple calculations to figure out how many calories you should consume to lose weight.

Maybe you have a few pounds to shed- maybe more than a few. After reviewing all of the diet plans out there, you've decided to settle for old-fashioned, yet effective, calorie counting and portion control. If you've looked over dietary guidelines, you may have noticed that some diets are designed for as little as 1,200 calories a day, while others for as many as 2,400 per day. You may be wondering how many calories you should eat.

If you want to lose weight, you want to make sure that you are taking in fewer calories than your body is expending. Food is fuel, and if your body is taking in less fuel than it needs to run, it is going to start tapping into stored energy and burn it up. That stored energy is fat. This may make a very low calorie diet tempting, as the thought is that it will foster a quicker weight loss, but this approach can actually be counterproductive.

When your body gets too little fuel, it begins to go into starvation mode. In starvation mode, your body is going to try and conserve energy. If you've ever been on a restrictive diet and suffered from head aches, fatigue, loss of energy, insomnia, a rumbling stomach, or irritability, you have experienced your body's starvation mode. This not only makes life extremely unpleasant and potentially endangers your health, but can make you too tired to exercise and cause your body to start burning muscle mass in addition to fat. To top it off, in starvation mode, you are most likely to run into a weight loss stall, as your body desperately tries to hang onto stored energy.

That is why, when on a diet, it is as important to eat enough foods as it is to avoid eating too much.


But just how much is enough? To find out your body's needs, you want to start by figuring out your Basal Metabolic Rate (BMR). This is the approximate number of calories you would need to maintain your current weight by just existing, without taking any physical activity into account. Once you have figured out your BMR, you can figure your rate of activity into the equation. The more active you are, the more calories you will need to take in.

The best way to calculate your approximate BMR is by using the Harris-Benedict Equation. This equation takes into account your gender, height, age, and current weight. What it does not take into account your muscle-to-fat ratio, so if you are particularly muscular, there is a good chance the formula will under-estimate your calories. Still, for those trying to lose weight, even though the BMR is an estimated number, it is a good place to begin.

The formula is as follows (and please remember the order of operations- calculate what is inside of the parenthesis first):

A Woman's BMR = 655 + (4.35 x W) + (4.7 x H) - (4.7 x A)

A Man's BMR = 66 + (6.23 x W) + (12.7 x H) - (6.8 x A)

In this formula, W = your current weight in pounds, H = your current height in inches, and A equals your current age in years. Therefore, if Edna is a 35 year old woman who is 5'8" tall and weighs 195 lbs would calculate as follows:

- 195 pounds multiplied by 4.35 = 848.25

- 68 inches multiplied by 4.7 = 319.6

- 35 years multiplied by 4.7 = 164.5

- formula: 655 + 848.25 + 319.6 - 164 = BMR of 1658.85

So Edna will need approximately base of 1650 calories to maintain her weight of 195 if she is not doing any exercise.


Once you know your BMR, you can plan the ideal intake your body needs for losing weight. Someone obese with a high BMR can reduce their intake by as much as 500 or 1000 calories per day; however, it should never be more than that. Most health care specialists recommend that women never go below 1,200 calories per day, and that men never go below 1,800. Remember also that the more physically active you are, the more calories you will need to intake.

Let's go back to Edna's example. She wants to drop 40 pounds, and has a BMR of 1650. She now has a choice: she can lower her caloric intake to below 1650, she can eat at least 1650 and increase her physical activity level, or she can do a combination of both.

Let's say Edna lives a sedentary lifestyle. She decides to decrease her caloric intake by 250 calories per day; this will give her a daily allowance of 1300 calories per day. Since one pound is equivalent to 3,500 calories, she will lose a pound every 2 weeks.

Instead of decreasing calories, Edna could opt to increase her activity so she will burn more calories. Every morning, she will go for a 45-minute walk at a moderate pace. At Edna's weight, this will burn approximately 250 calories per day. Thus, Edna can eat her 1650 calories per day and still lose her half pound per week.

A third option, and the most effective option at that, would be for Edna to decrease her caloric intake, as well as increase her physical activity level. That way, Edna can eat more nutritious foods and feel satisfied, get the benefits of a blood-pumping cardiovascular work out every day, and lose weight faster than if she just did one or the other. Lowering her intake by 250 calories per day, and burning off approximately 250 calories per day walking gives Edna a total of 500 calories per day, or roughly 1 pound per week.


Once you have calculated your BMR and decided upon a caloric intake, just how do you use it to guide your portions? Most health care specialists recommend that 45-65% of your diet come from carbohydrates, from 10-35% from protein, and 20-35% from fat. So, if Edna wanted to balance her diet, she might decide that about 50% of her intake would be carbohydrates, 30% would be protein, and, since she wants to lose weight, she would keep fat to a minimum of 20%.

But how would this translate to the plate in calories? Remember these simple formulas:

Calories = carbs/4

Calories = protein/4

Calories = fat/9

If 50% of Edna's calories were carbohydrates, and Edna were eating 1300 calories per day, then 650 calories per day should come from carbohydrate rich sources. 650 calories divided by 4 equalss 182.5 grams of carbohydrates per day, approximately. For protein, Edna would figure out that 30% of her 1300 calories per day is 390, and 390 calories divided by 4 equals 97.5 grams of protein per day. To figure out her grams of fat, she would figure %20 of 1300 equals 260 calories from fat; so 260/9 is roughly 28 grams of fat per day.

Of course, these numbers can be varied slightly, but they will give you a good guideline when meal planning.


Are you working out harder now that you've lost some weight, and finding yourself hungry more often? It may be time to raise your caloric intake- even if you are not at your goal, a slight raise in calories can compensate for the extra energy you are burning.

Have you come to a plateau, and found your weight loss stalled? Perhaps you need to lower your caloric intake more, now that your BMR is lower. Or, perhaps you are building muscle, and your caloric intake is no longer enough.

As you progress on your weight loss journey, you may wish to occasionally re-evaluate your plan, and adjust it as necessary. Remember that these numbers are rough estimates, and should not be considered written in stone. If your body is not losing weight, or dropping weight too rapidly, don't be unwilling to change your program because of what your calculations say. Still, if you had no idea where to start with your diet program, these calculations will give you a general idea of where to begin.

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