Signed weight change and entered goal weight
Percentage change remains comparable when both weights use the same unit. Weight lost and goal weight follow the selected pounds or kilograms. The calculation does not distinguish fat, muscle, fluid, or other sources of body-weight change.
For a separate body-mass-to-height calculation, the BMI Calculator uses the current weight and height.
The formula
Starting weight is the reference denominator. A positive result means current weight is lower; a negative result means it is higher. The goal is a user-entered arithmetic comparison, not a recommended weight or loss rate.
Worked example
Starting at 200 lb and currently weighing 180 lb gives 20 lb lost and a 10% reduction from the start. An entered 5% loss goal corresponds to 190 lb. If current weight were 220 lb, the displayed loss would be −10%, meaning a 10% gain.
How to use this calculator
- Enter starting and current weight in matching units.
- Select pounds or kilograms and enter any percentage goal you want to compare.
- Calculate the signed percentage; a negative loss indicates a gain.
Choose a consistent starting record
Use a clearly dated starting weight and compare it with a current measurement made under similar conditions. Different scales, clothing, meals, hydration, and timing can influence individual readings. A trend across comparable records is usually more informative than comparing inconsistent measurements. The tool stores no series and calculates only the two weights entered.
Separate arithmetic from a health target
A percentage goal converts a selected relative change into a weight value. It does not establish whether losing weight is appropriate for an individual. Medical conditions, medicines, age, and other circumstances can affect body mass. Unexpected or unintentional weight changes require context rather than an automatic interpretation based solely on a percentage.
Assumptions & limitations
What this calculation assumes
- Starting and current weights use the same unit and comparable measurement conditions.
What to keep in mind
- Excludes body composition, time-based progress, recommended targets, and medical interpretation.
Common questions
Why is percentage loss negative?
Current weight exceeds the starting weight, so the signed result describes a gain.
Which weight belongs in the denominator?
Use the starting weight. Dividing by the current weight answers a different question and changes the percentage.
Does this measure fat loss?
No. It measures change in total scale weight. Fat, muscle, fluid, and other changes cannot be separated by these inputs.
Sources & further reading
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