Calories etc: How many calories do I need?

If you have a calculator, then you can figure out how many calories you need. Sure, there are dozens of online calculators, but either of the following expert-recommended mathematical equations are super accurate for calculating your calorie needs. One (the Harris-Benedict equation) uses the metric system. Both formulas yield a similar result.

What is Basal Metabolic Rate (BMR)?

The first step for either formula is to calculate your BMR. This is, quite simply, the minimum amount of energy (in calories) you need daily to sustain life. BMR factors in not only your height and weight, but your age. BMR declines every decade beyond age 30, some say up to 10%. This impacts your calorie needs – you need fewer calories daily to maintain your weight as you age. Calculating BMR is only the first step. You need to multiply that number by a physical activity level (PAL), also known as an activity factor. Choose this number based upon your exercise level and lifestyle (active or sedentary job).

Calculations for calories needed

Harris-Benedict Equation:
Men = 66 + (6.3 x weight in lbs) + (12.9 x height in inches) – (6.8 x age in years) = BMR
Women = 655 + (4.35 x weight in lbs) + (4.7 x height in inches) – (6.8 x age in years) = BMR

Mifflin-St. Jeor Equation:
Men = 10 x (weight in kg) + (6.25 x height in centimeters) – (5 x age in years) + 5 = BMR
Women = 10 x (weight in kg) + (6.25 x height in centimeters) – (5 x age in years) – 161 = BMR

The next step is to multiply your BMR by the most suitable physical activity factor (keep in mind that most individuals overestimate their level of physical activity):

Sedentary = BMR x 1.2
Light activity = BMR x 1.375
Moderately active = BMR x 1.55
Very active = BMR x 1.725
Extremely active/Athletic = BMR x 1.9 or more

Using the Harris-Benedict Equation, the BMR for a 40 year-old man, 5’10” and 164 lbs = 1,730 calories
Using the Mifflin St-Jeor formula, the BMR for the same man = 1,661 calories

Calories to lose or gain weight

Now, if you want to gain or lose weight, you need to go a step farther. To lose 1 lb in one week, you need to create a calorie deficit of 3,500 calories. The best way to do this is to decrease your daily caloric intake by 500 calories. You can do this by cutting down on the calories you consume and/or increasing the amount of calories you burn by increasing your exercise intensity, frequency and/or duration. The reverse is true for gaining weight.