Calculating your weight loss is a great way to find out how far you have come.
To calculate the percentage of weight lost, grab a calculator and follow these steps.
The quick and easy way
Your percent weight change is a very quick and easy snapshot of your weight loss as a whole. This quick math that will compare your pre-op weight to your current weight.
(Pre-op weight – Current weight) / (pre-op weight) x 100 = % body weight change
Example: Your pre-op weight was 320 lbs, and your current weight is 200 lbs
(320-200) / (320) x 100 = 37% total body weight loss
The full picture
Calculating your weight loss based on your excess body weight – instead of your weight as a whole – is what is typically used in the bariatric clinic.
It requires a few extra calculations, but it gives us more precise information regarding where you are in your weight loss journey compared with your own healthy range.
There are a few steps, but don’t be intimidated, just follow along:
In order to determine your excess body weight, you'll need to find the weight that would put you at a healthy Body Mass Index (BMI) of 25. A healthy BMI ranges from 18-24.9 (for the purpose of this calculation, we will round it to 25).
25 x (height in inches x height in inches / 703) = Weight in lbs to be at a BMI of 25
Example: You are 5’7” (67 inches; Remember, there are 12 inches in a foot)
25 x (67 x 67/703) = A healthy weight starts at 159.6 lbs
After you have calculated the weight that puts you at a healthy BMI, now it is time to calculate your excess body weight.
Pre-op weight – weight to be at a BMI of 25 = Excess body weight
Example: Your pre-op weight was 320 lbs. and you are 5’7”
320 – 159.6 = 160.4 lbs of excess body weight
To calculate the percentage excess body weight loss, use the following formula.
(Number of lbs you lost / excess body weight) x 100 = Percent of excess body weight loss
Example: Your excess body weight was 160.4 lbs; You lost 120 lbs from 320 lbs and your current weight is 200 lbs.
(120 / 160.4) x 100 = You lost 74% of excess body weight
With these calculations in place you will be able to better track your progress and continue to work toward your goals.