Whether you're trying to lose 5 pounds or 50, tracking your weight loss helps keep you motivated. It helps you keep track of your progress toward your ultimate goals, even if you're not seeing huge results in the mirror from day to day. While you can measure the pounds you lose, you can also count the percentage of weight you shed -- or your percentage of body fat lost. It's easy to calculate your weight loss percentage at home, using pen and paper or a calculator, though you might have to consult a professional to measure your body fat percentage.
Calculating Your Weight Loss Percent
Choose one day a week for your "official" weigh-in. Ideally, you should weigh yourself first thing in the morning, after going to the bathroom, to get a weight measurement that isn't influenced by your food intake for the day. You'll need to complete at least two weigh-ins to calculate your weight lost.
Calculate your weight loss percent for the week using the following equation:
Weekly Weight Loss Percent = [ (Last week's weight - This week's weight) / Last week's weight ] x 100.
You can use a similar equation to figure out how much weight you lost over a longer period by comparing your current weight to your starting weight:
Total Weight Loss Percent = [ (Starting weight - Current weight) / Starting weight ] x 100.
This equation will help you figure out what percentage of your body weight you've lost, total -- not just in the last week.
A Real-World Example
Don't worry if those equations look complicated -- once you get started using real numbers, the math looks a lot simpler.
Take, for example, a 150-pound woman looking to lose weight. If she loses 2 pounds in her first week -- lowering her weight to 148 pounds -- she could calculate her percentage of weight loss like this:
Weekly Weight Loss Percent = [ (150 - 148) / 150 ] x 100
Weekly Weight Loss Percent = [ 2 / 150 ] x 100
Weekly Weight Loss Percent = 1.33
If, the next week, she loses another 2 pounds -- going from 148 to 146 pounds -- she would calculate her weekly weight loss like this:
Weekly Weight Loss Percent = [ (148 - 146) / 148 ] x 100
Weekly Weight Loss Percent = [ 2 / 148 ] x 100
Weekly Weight Loss Percent = 1.35
Once she reaches her goal weight -- let's say it's 125 pounds -- she could calculate her total percentage of weight loss using this equation:
Total Weight Loss Percent = [ (150 - 125) / 150 ] x 100
Total Weight Loss Percent = [ 25 / 150 ] x 100
Total Weight Loss Percent = 16.67
Over the course of her entire weight loss journey, she's lost 25 pounds, which is 16.67 percent of her original weight.
Weight Loss Percent Vs. Fat Loss Percent
While it's easy to figure out your percentage of weight loss, not all of that weight necessarily comes from fat. While you'll lose fat as you shed weight, you might also lose water weight and muscle tissue. That means that your percentage of fat loss might be different from your overall weight loss -- especially if you lose weight via fad dieting, which means you'll generally lose more muscle than when you lose fat in a slow-and-steady manner.
Unfortunately, it's more complicated to figure out your body fat loss at home -- you'll need to consult a professional. A doctor or sports clinic professional can use skinfold calipers or body scans to estimate your fat levels, and repeated readings can help you see how much of your weight loss comes from fat. If you're worried about your body fat levels, professional testing might be worth the investment, since a high body fat percentage can cause health issues even if you're at a healthy weight.
What Percentage to Expect
While you should aim for slow weight loss -- generally, at a rate of 1 to 2 pounds a week -- there's no standard weekly weight loss percentage recommendation. That's because, when you lose 1 to 2 pounds a week, your weight loss percentage will vary depending on your starting weight. For example, a 160-pound person who loses 2 pounds will have lost 1.25 percent of his body weight, while a 180-pound person who loses 2 pounds will have shed 1.11 percent of the body weight. So while calculating your weight loss percentage can be helpful, you should still aim for a weight loss of 4 to 8 pounds each month.
There is a recommended rate of fat loss, however -- you should lose a maximum of 1 percent of your body fat each month, according to the American Council on Exercise.