By Zencalcy Editorial TeamLast reviewed About us
Weight loss percentage expresses a change in weight relative to where you started. It is more useful than kilograms alone when comparing progress between people of different sizes. A 5% loss is often used as a clinically meaningful threshold.
See how much weight you have lost as a percentage.
Weight loss % = (starting weight − current weight) ÷ starting weight × 100
A positive result is weight loss; a negative result is weight gain. Percentage change is sensitive to the starting value, so a 5 kg loss is a larger percentage for a lighter person. Clinical guidance often treats 5–10% loss as meaningful.
| Symbol | Meaning |
|---|---|
| Starting weight | Weight at the beginning of the period. |
| Current weight | Weight now, measured the same way. |
| Weight loss % | Change divided by starting weight, as a percentage. |
(90 − 81) ÷ 90 × 100 = 10.0%. The same 9 kg loss from a 120 kg start would be 7.5%, showing why percentage is useful for comparisons.
Weight change is not comparable across body sizes. Losing 5 kg is a major change for a 60 kg person and a modest one for a 120 kg person. Expressing the change as a percentage of starting weight puts everyone on a similar scale, which is why clinical trials and guidelines use it. The measure still has limitations. It cannot tell you whether the lost weight was fat, muscle or water. Rapid early loss is often partly water, and a high-protein diet can shift scale weight without changing fat mass much. For a fuller picture, track waist circumference and, if possible, body composition alongside weight. Percentage change is also sensitive to the reference point: if you choose a temporary low or high weight, the result can flatter or exaggerate progress. Pick a clear starting point and compare like with like.
Continue with the ABSI Calculator (A Body Shape Index), Adjusted Body Weight Calculator, or the BAI Calculator (Body Adiposity Index) — or browse more body measurements tools and all health calculators.
Also see the Body Fat Calculator.
Guidelines often cite 5–10% of starting weight as meaningful for improving blood pressure, glucose and lipids. The right target depends on your health and circumstances.
Every result is a screening estimate from published anthropometric equations, not a diagnosis or a measurement of body composition. Tape measurements should be taken snugly against the skin without compressing it, at the landmarks named in each tool. Equations were derived in specific populations and can be less accurate for athletes, older adults, children, pregnant people and people with significant oedema.
Reference material used to build and check this calculator:
Last reviewed: September 2026. See how we build and check every tool on the about page.
Content updated: September 2026