Calculating your weight lost is straightforward once you know the Weight Loss Percentage formula and what each input means. This guide explains the method in plain language, walks through a manual calculation, and gives worked examples you can follow — then you can do it instantly with the Weight Loss Percentage Calculator.
What is Weight Loss Percentage?
The Weight Loss Percentage calculation tells you your weight lost from a few simple inputs. The figure you are solving for here is the weight lost, expressed in percent.
The Weight Loss Percentage formula
The core formula is:
Weight lost = (Starting weight - Current weight) ÷ Starting weight × 100Here is what each input means:
- Starting weight — a value measured in kg. Example: 90 kg.
- Current weight — a value measured in kg. Example: 81 kg.
How to calculate it step by step
- Write down the starting weight (for example, 90 kg).
- Write down the current weight (for example, 81 kg).
- Apply the formula above to get your weight lost.
- Double-check the result with the Weight Loss Percentage Calculator.
Worked examples
Example 1
| Input / Output | Value |
|---|---|
| Starting weight | 90 kg |
| Current weight | 81 kg |
| Weight lost | 10.00% |
| Weight change | 9.0 |
With starting weight of 90 kg and current weight of 81 kg, the weight lost works out to 10.00%.
Example 2
With starting weight of 180 kg and current weight of 81 kg, the weight lost works out to 55.00%.
| Result | Value |
|---|---|
| Weight lost | 55.00% |
| Weight change | 99.0 |
Example 3
With starting weight of 45 kg and current weight of 81 kg, the weight lost works out to -80.00%.
| Result | Value |
|---|---|
| Weight lost | -80.00% |
| Weight change | -36.0 |
Tips for an accurate result
- Keep your units consistent — mixing, say, months with years or grams with kilograms is the most common source of error.
- Round only at the very end. Rounding inputs early can shift the final answer noticeably.
- Re-run the numbers whenever an input changes, rather than estimating from an old result.
- These figures are general estimates, not medical advice — check with a qualified professional before acting on them.
Prefer not to do the maths by hand? — the Weight Loss Percentage Calculator does it instantly, for free, with the formula and a worked example built in.
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