How to calculate your weight loss percentage
Your weight loss percentage is the weight you have lost divided by your starting weight, multiplied by 100. If you began at 100 kg and now weigh 95 kg, you have lost 5%. The weight loss percentage calculator does the arithmetic in kilograms or pounds.
The formula, step by step
Percentage lost = (starting weight minus current weight) ÷ starting weight × 100
Suppose you started at 84 kg and now weigh 79.8 kg. Subtracting gives 4.2 kg. Divide 4.2 by 84 to get 0.05, then multiply by 100 to get 5%.
| Starting weight | Current weight | Amount lost | Percentage lost |
|---|---|---|---|
| 100 kg | 95 kg | 5 kg | 5% |
| 84 kg | 79.8 kg | 4.2 kg | 5% |
| 200 lb | 190 lb | 10 lb | 5% |
| 80 kg | 78 kg | 2 kg | 2.5% |
These are arithmetic examples, not suggested targets. Keep both weights in the same unit. A conversion from kg to lb changes both numbers by the same factor, so the percentage stays the same.
Keep your starting point consistent
Use the same starting weight when comparing your progress over time. A change from 100 kg to 90 kg is 10% of the original weight. A later change from 90 kg to 81 kg is another 10% of that new starting weight. Together they are 19% of the original 100 kg, not 20%.
Write down the starting date as well as the weight. A percentage alone cannot distinguish a change over a week from a change over a year.
What if your weight increased?
The formula produces a negative percentage when the current weight is higher. Going from 80 kg to 82 kg gives minus 2.5% weight loss, which is more naturally described as a 2.5% gain. Our calculator labels it as a gain. If the two weights are equal, it shows no change.
Weight loss percentage is not body fat percentage
This calculation uses total scale weight. It cannot tell how much of the difference came from fat, muscle, water or other changes. Body fat percentage asks a different question: how much of your current weight is estimated to be fat. Our body fat guide explains one estimation method and its limits.
For a running record, the free weight tracking spreadsheet keeps readings and weekly averages together. Compare the same kind of reading each time rather than switching between a single weigh-in and an average.
This article is general information, not medical advice. Talk to a doctor before a big change to what you eat or how you train, and especially if you are pregnant, under 18 or have a health condition.