Weight loss percentage calculator

What is weight loss percentage?

Weight loss percentage expresses how much weight you have lost relative to where you started, rather than as a raw number. Losing 20 units means something very different for someone who started at 200 than for someone who started at 120, and a percentage makes that comparison fair. It is the figure commonly used in weight-loss challenges and clinical settings because it puts everyone on the same scale regardless of body size.

This calculator takes your initial weight and your current weight (in the same unit) and returns both the total weight lost and the percentage of your original weight that represents.

Formula

With initial weight $W_i$ and current weight $W_c$, the weight lost and the loss percentage are:

The unit cancels out in the percentage, so it works with kilograms, pounds, or any consistent unit as long as both weights use the same one.

How to use

1. Enter your initial weight — your weight at the start.
2. Enter your current weight in the same unit.
3. Read off the weight lost and the weight loss percentage. Results appear once your initial weight is greater than zero and a current weight is filled in.

Worked example

Suppose you started at 200 and now weigh 180 (same unit):

So you have lost 20 units, which is 10% of your original weight.

FAQ

Does the unit matter? No, as long as both weights use the same unit. Because the percentage is a ratio, the unit cancels out — kilograms and pounds give the same percentage for the same proportional change.

What if my current weight is higher than my initial weight? The result becomes negative, which represents a weight gain rather than a loss. For example, going from 180 to 200 yields -11.1%.