Why use a percentage?
A percentage puts an absolute change in context. Losing 5 kg from 100 kg is a 5% change, while losing 5 kg from 60 kg is approximately 8.3%. The percentage alone does not determine whether that change is appropriate.
The percentage-change formula
Subtract current weight from starting weight, divide by starting weight, and multiply by 100. A positive result indicates loss, zero indicates no change, and a negative result indicates gain.
How to use this calculator
- 1Enter a positive starting weight.
- 2Enter current weight using the same unit.
- 3Calculate the percentage and consider the time period and circumstances of the change.
Understanding your result
This is a description of recorded change, not a forecast or body-fat measurement. Use consistently measured weights or comparable averages. The speed and cause of a change matter alongside its percentage.
Assumptions & limitations
- The calculation cannot separate fat loss from changes in water, muscle, or other tissue.
- It does not assess the cause or health significance of unintentional weight change.
Frequently asked questions
Why is my result negative?+
Current weight is higher than starting weight, so the formula produces a negative loss percentage. That describes weight gain, not a calculation error.
Does the unit affect the percentage?+
No. The ratio is the same with kg or lb if both weights use the same unit.
Is 5% weight loss the same as five percentage points of body fat?+
No. This result compares total body weights. A change in body-fat percentage describes a different ratio and needs body-composition information.
Can I use weekly average weights?+
Yes. Comparing averages collected in a consistent way can reduce the influence of one unusual scale reading.
