Knowing how many calories you need per day helps you determine what you need to eat to lose, gain or maintain your weight. You'll need to know your basal metabolic rate to calculate the amount of calories needed. The BMR takes into account gender, weight, height and age. The Harris Benedict Equation is an accurate way of determining calories needed based on your BMR and activity level.
Step 1
Complete one of the following equations to determine your BMR, depending on your gender:
Women: 655 + (4.35 x weight in pounds) + (4.7 x height in inches) - (4.7 x age in years)
Men: 66 + (6.23 x weight in pounds) + (12.7 x height in inches) - (6.8 x age in years).
Step 2
Determine your daily activity level.
Step 3
Multiply your BMR by one of the following numbers, depending on your activity level:
Little to no exercise: 1.2
Light exercise one to three days per week: 1.375
Moderate exercise three to five days per week: 1.55
Hard exercise six or seven days per week: 1.725
Very hard exercise daily and/or physically demanding job: 1.9
Step 4
Multiply the amount of calories you require daily by 0.30 to learn how many of your calories should be from fat.
Step 5
Divide the total fat calories by 9 to determine how many fat grams this amounts to.
Tips and Warnings
- You can also calculate your BMR and calories needed on websites such as BMI Calculator and the Mayo Clinic (see Resources). Consult your doctor before stating any diet or exercise program.
- The BMR and Harris Benedict formulas do not take lean body mass into account. If you're very muscular, this method can underestimate calories needed, and if you're overweight, the method can overestimate calories needed. Do not consume less than 1,200 calories per day if you're a woman, or 1,500 calories per day if you're a man.
Things You'll Need
- Calculator
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