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How to Calculate BMI & Find Calorie Intake

Body Mass Index (BMI), a measure of weight and height, is considered a fairly reliable indicator of body fatness in the average person. In the average adult, a BMI below 18.5 is considered underweight; 18.5 to 24.9 is considered normal; 25.0 to 29.9 is considered overweight; and 30.0 and above is considered obese. BMI determines daily calorie intake--an individual may need to increase or decrease his intake to reach a normal BMI. Daily calorie requirements vary by individual, and those wishing to reach a healthy BMI need to calculate their specific calorie needs.

Things You'll Need

  • Bathroom scale
  • 8-foot tape measure
  • Ruler
  • Masking tape
  • Calculator
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Instructions

  1. Calculate BMI

    • 1

      Weigh yourself. Place the scale on a hard, even surface. Remove your shoes and stand with both feet evenly on the scale.

    • 2

      Record the first reading, step off the scale and weigh yourself two more times. If the number changes by a pound or more, add all the numbers together and divide by three.

    • 3

      Stand against a wall with your heels against the baseboard and your hips, shoulders and the back of your head against the wall. Stand tall, but keep your spine neutral.

    • 4

      Have a friend place the flat of a ruler on top of your head so that the end is touching the wall. Mark the wall with a piece of masking tape at the height of the ruler.

    • 5

      Put the end of the tape measure on the floor and run the tape up to the bottom of the piece of masking tape. Write down the number in inches.

    • 6

      Use the calculator to divide your height, in inches, by your weight, squared, and multiply the result by 703. For example: If you are 66 inches tall (5'6") and weigh 150 lbs., you would use the following equation:

      150/(66)2 = 150/4356 = 0.034; 0.034 x703 = a BMI of 24.2

    Calculate Basal Metabolic Rate (BMR) and Daily Calories

    • 7

      Use the calculator to find the female BMR--the minimum number of calories you need for basic survival.

      Multiply your weight by 4.35, your height, in inches, by 4.7 and your age by 4.7. For a 40-year-old woman at 5'6" and 150 lbs., you would have the following: (150 x 4.35 = 652.5), (66 x 4.7 = 310.2), (40 x 4.7 = 188).

      Add 655 to the height and weight and subtract your age: 655 + 652.5 + 310.2 -- 188 = a BMR of 1,430 (1,429.7).

    • 8

      Use the calculator to find the male BMR.

      Multiply your weight by 6.23, your height, in inches, by 12.7, and your age by 6.8. For a 40-year-old man at 5'6" and 150 lbs., you would have the following: (150 x 6.23 = 934.5), (66 x 12.7 = 838.2), (40 x 6.8 = 272).

      Add 66 to the height and weight and subtract your age: 66 + 934.5 + 838.2 -- 272 = a BMR of 1,567 (1,566.7).

    • 9

      Calculate your daily calories based on your activity level. For example, sedentary individuals get little to no exercise, while extra-active people have physically active jobs or exercise for several hours a day every day. Sedentary individuals should multiply the BMR by 1.2. Lightly active people need to multiply the BMR by 1.375. Moderately active people should multiply the BMR by 1.55. Very active people would multiply the BMR by 1.725. Extra-active people should multiply the BMR by 1.9.

      A moderately active man would use the following equation: 1,567 x 1.55 = a maximum of 2,429 calories a day.

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