How to Figure Out Your BMI & Caloric Needs

Use the same scale for an accurate measurement each time.

Use the same scale for an accurate measurement each time.

There's a lot of buzz surrounding the body mass index, or BMI, and just what that number means. From physicians to dietitians, growing concern over burgeoning waistlines have health professionals everywhere obsessed with those three little words -- and for good reason. Your BMI tells your physician whether you are at a healthy weight, overweight or underweight, and knowing this can help identify whether you're at risk for disease or complications. BMIs are dependent on two factors, height and weight. Determining your BMI requires a calculation involving the two numbers.

Calculating Your BMI

Place your scale on a level surface. Stand on the scale and record your weight on the paper. Determining accurate body weight is best done first thing in the morning before you've eaten, and with as few items of clothing on as possible.

Secure the measuring tape to a door jam or wall, if you have to do so, making sure the beginning of the tape starts at the floor. If someone is assisting you, they can hold the measuring tape for you.

Stand against the measuring tape and note your height. Convert this number to inches. If you measured 5'3", you would stand 63 inches tall. For each foot of your height, add 12 inches, tacking on the additional inches to the total. Log this number for easy reference.

Grab your calculator and multiply your logged weight by 703. Then, take your height in inches and divide it into the answer. Third, take that answer and again, divide it by your height. The resulting number is your BMI.

Finding Your Daily Caloric Need

Calculate your basal metabolic rate to determine how many calories you need for your activity level in order to lose or maintain weight. Unlike the BMI formula, the BMR formula varies for men and women.

Multiply 4.35 to your total weight in pounds, and then add this number to 655 for women. Next, multiply your height in inches with 4.7 and add that to the previous value. You should have a large number. Set it aside, take your age and multiply that by 4.7, as well. Take the larger number and subtract it from this last number. That number, while still big, is your BMR.

Determine your activity level and calculate that into your BMR to find your caloric needs. For sedentary lifestyles, multiply your BMR by 1.2. If you get in one to three days if light exercise per week, multiply by 1.375. Three to five days of moderate exercise of sport activities per week requires you to multiply by 1.55. If you lead an active lifestyle, exercising six to seven days a week, multiply by 1.725. And vigorous, physically active lifestyle -- athletes in training for example or those with physical jobs -- can multiply by 1.9.

Consume the number of calories in step 3 to maintain your current weight, or eliminate 500 calories from your daily diet to lose 1 pound per week.

Items you will need

  • Bathroom scale
  • Paper to log weight and height
  • Pencil
  • Measuring tape
  • Calculator


  • As you lose weight, recalculate both your BMI and caloric need to readjust your diet and exercise level.

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About the Author

Having studied at two top Midwestern universities, Catherine Field holds degrees in professional writing and patient safety. Writing since 2000, Field has worked with regional newspapers while publishing fiction online. She conducts medical communication research at a Midwestern medical institution and is slated to write a book based on her research findings.

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