Calculate the percentage difference between a starting weight and a later weight. Use matching units and comparable measurement conditions. This describes an observed change; it does not set a goal or tell you how quickly to lose weight.
How to calculate percentage of weight loss
(Starting weight − current weight) ÷ starting weight × 100. The starting value is the denominator. A 10 lb decrease is a different percentage of 150 lb than of 250 lb. Kilograms work with the same formula because the units cancel.
| Start → current | Calculation | Observed change |
|---|---|---|
| 200 → 190 lb | (200 − 190) ÷ 200 × 100 | 5% decrease |
| 80 → 76 kg | (80 − 76) ÷ 80 × 100 | 5% decrease |
| 80 → 84 kg | (80 − 84) ÷ 80 × 100 | −5%, meaning a 5% increase |
| 80 → 80 kg | (80 − 80) ÷ 80 × 100 | 0% change |
Put the result in trend context
A percentage does not distinguish fat, fluid, muscle or the contents of your digestive system. Compare readings from the same scale and similar conditions; see NHS weighing guidance. For a confusing short-term pattern, use the two-week consistency check-in.
Unintended weight loss or a rapid unexplained change deserves clinical review. Do not use this number to make an eating plan more restrictive. Inputs are not stored after reload; no account is needed.