Weight Loss Percentage Calculator

What percent of your current weight must you lose to reach your goal weight?

Weight loss (and weight gain) goals are often measured in percents rather than net pounds or kilograms. This allows for easier comparison between people with different starting weights.

For example, if a person weighs 380 and drops down to 260, the loss of 120 pounds represents a 31.6% reduction in weight. Now consider another person who starts out weighing 260 pounds and slims down to 140 pounds. While the total amount lost is the same in both cases, the second person has reduced by 46.2%.

You can use the calculator on the left to calculate percent change from your starting weight, current weight, to your goal weight. Charting the percentage of weight lost at various stages can motivate you and help you achieve your desired weight.

Since percents are dimensionless, it does not matter if you enter your weight in pounds or kilograms, so long as the units are the same for each of the three fields.

Example 1: In January Mike weighed 180 kg and set a goal of weighing 99 kg by December. It is currently June and Mike weighs 151 kg. So far, he has lost (180-151)/180 = 16.1% of his starting weight.

To reach his goal of 99 kg, he needs to lose (151-99)/151 = 34.4% of his current weight.

If he achieves his goal of weighing 99 kg by December, he will have lost (180-99)/180 = 45% of his starting weight.

Notice that the percents are not additive, 16.1 + 34.4 does not equal 45. In order to calculate the percent decrease for each date range, you must use the formula

(Weight_old - Weight_new)/Weight_old


Example 2: Mike's son John wants to bulk up and gain weight. In January he weighed 46 kg and set a goal to weigh 70 kg by December. It is currently June and John weighs 62 kg. So far, he has gained (62-46)/46 = 34.8% of his beginning weight.

To meet his goal of weighing 70 kg, he needs to gain (70-62)/62 = 12.9% of his current weight.

If he reaches his goal in December, he will have gained a total of (70-46)/46 = 52.2% of his starting weight.

Notice here as well that the percents are not in an additive relation to one another. To calculate percent increase, you must use the formula

(Weight_new - Weight_old)/Weight_old

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