Calculating Your BMI and BMR to Achieve Your Ideal Weight

Registered Dietician

| 3 min read

Person measuring their waist
So, how can you tell if your weight falls within a healthy range? Read more and you will be able to calculate your ideal weight, and learn how to reach it.

Calculate your BMI

BMI, or body mass index, confirms your height to weight ratio and provides the information needed to successfully manage your weight.
There are many online tools that will calculate your BMI, or try this formula:
BMI = (Weight in Pounds / (Height in inches x Height in inches)) x 703
SAMPLE: 42 year old woman, weighing 188 pounds and is 5’4″ (64 inches)
  • BMI = (188 / (64 x 64)) x 703
  • BMI = 32.2
Keep in mind:
  • Underweight = <18.5
  • Normal Weight = 18.5-24.9
  • Overweight = 25-29.9
  • Obese = > 30
Now that you know your BMI, you can now calculate your BMR to pinpoint your calorie needs.

Calculate your BMR: How Many Calories Should I Eat?

The BMR is your basal metabolic rate, and confirms what kind of metabolism you have. Once you know your BMR, it will take you to the next steps of calculating your suggested intake of calories.
Use online tools to figure out how many calories you should be consuming daily, or use the following Harris-Benedict equation to calculate your BMR by hand.
  • Women: BMR = 655 + (4.35 x weight in pounds) + (4.7 x height in inches) – (4.7 x age in years)
  • Men: BMR = 66 + (6.23 x weight in pounds) + (12.7 x height in inches) – (6.8 x age in years)
SAMPLE: 42 year old woman, weighing 188 pounds and is 5’4″ (64 inches)
  • BMR = 655 + (4.35 x 188) + (4.7 x 64) – (4.7 x 42)
  • BMR = 655 + 817.8 + 300.8 – 197.4
  • BMR = 1576.2
This number tells us the amount of calories the person in this sample would need to function.

Physical Activity Factor

Now we must calculate the right amount of calories that you should be consuming.
Use this tool to properly calculate your calories by multiplying the BMR x the physical activity factor, or calculate by hand by following these physical activity factors:
  1. If you are sedentary (little or no exercise): Calorie-Calculation = BMR x 1.2
  1. If you are lightly active (light exercise/sports 1-3 days/week): Calorie-Calculation = BMR x 1.375
  1. If you are moderatetely active (moderate exercise/sports 3-5 days/week): Calorie-Calculation = BMR x 1.55
  1. If you are very active (hard exercise/sports 6-7 days a week): Calorie-Calculation = BMR x 1.725
  1. If you are extra active (very hard exercise/sports & physical job or 2x training): Calorie-Calculation = BMR x 1.9
SAMPLE: 42 year old woman lives a sedentary life with little exercise. Therefore we multiply her BMR x 1.2 = 1575.2 x 1.2 = 1891.44
This means our sample would need about 1,890 calories to maintain her weight; however, we know that she wants to lose weight. For weight loss one must subtract 500 calories from this number: (example 1890-500 = 1391 calories per day to lose weight)
If you come to the realization that you are underweight, you can add 500 calories to the BMR multiplied by the physical activity factor number.
These calculations can help you get from where you are to where you hope to be. Let us know what you find out.
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Photo credit: Ralf Geithe

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