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Weight-Loss Percentage Calculator: Formula and Worked Examples
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Weight loss percentage = (starting weight − current weight) ÷ starting weight × 100. Use the same unit for both weights. For example, going from 80 kg to 76 kg is 4 ÷ 80 × 100 = 5%. This describes the change relative to your own starting weight; it is not a body-fat percentage.
Weight-loss percentage calculator
Try the example, then change the assumptions to explore your own estimate.
Use the same unit for both weights: kg or lb.
Illustrative example result
Weight loss: 5%
Relative to starting weight, not body-fat percentage.
Calculations stay on this page. Your input values are not sent to analytics.
Calculate weight loss in percentage: examples
| Starting weight | Current weight | Change | Percentage loss |
|---|---|---|---|
| 80 kg | 76 kg | 4 kg | 5% |
| 200 lb | 190 lb | 10 lb | 5% |
| 150 lb | 140 lb | 10 lb | 6.67% |
| 250 lb | 240 lb | 10 lb | 4% |
How to calculate your percentage weight loss
Subtract current weight from starting weight, divide by the starting weight, then multiply by 100. You do not need to convert pounds to kilograms if both values are already in pounds. A zero or negative starting weight is invalid; if current weight is higher, the signed result represents gain rather than loss.
Why the starting weight is the denominator
Going from 200 lb to 190 lb is a 10 lb decrease, or 5% of 200 lb. Dividing by 190 instead gives about 5.26%, which answers a different question. Keep the baseline fixed when you compare progress against the original starting point.
The same number of pounds is not the same percentage for everyone. A 10 lb change from 150 lb is about 6.67%; from 250 lb it is 4%. That does not establish whose change was healthier or whether it was body fat, water or lean tissue.
Common calculation mistakes
| Mistake | Why it fails | Correction |
|---|---|---|
| Divide by current weight | Changes the baseline | Divide by starting weight |
| Mix kg and lb | Compares incompatible inputs | Use the same unit |
| Call the result body-fat loss | Scale weight includes more than fat | Describe it as body-weight change |
| Reset the baseline each week | Breaks a comparison with the original start | Record the chosen baseline date |
Use the percentage as context, not a daily score
Compare weights measured under similar conditions and look at trends. Short-term changes can reflect fluids, digestion and measurement conditions. Percentage change alone does not tell you whether your eating pattern is adequate or whether unintentional weight loss needs medical evaluation.
For the daily food habits behind your trend, try BiteCal. Its convenient paid AI scan starts with a photo, lets you review the food and portion, and records calories and macros. Free features, a clear daily overview and the cute white bear make regular logging more enjoyable. An app does not determine whether a particular rate of weight change is medically appropriate.
Reference check date
Sources and calculations checked October 27, 2026.
Frequently asked questions
Is percentage weight loss the same as body-fat percentage?
No. Percentage weight loss compares two scale weights. Body-fat percentage estimates the share of body mass that is fat; it cannot be calculated from those two weights alone.
Does a negative result mean the formula is broken?
No. If current weight is higher than starting weight, the signed loss formula is negative. Report that as a gain rather than silently converting it into a positive loss.
