What this calculator does
A weight loss percentage calculator answers one specific question: of the weight you started at, what share has come off. It takes a starting weight and a current weight and returns the difference as a percentage of the starting figure, which is a more useful comparison than the raw number of kilograms or pounds when judging change relative to body size.
This is a descriptive figure, not a goal. It tells you what has happened between two weigh-ins, and nothing about whether that rate of change is appropriate, healthy or worth continuing. For anything beyond a plain read of the numbers, a doctor or dietitian who knows your history is the right person to ask.
The formula
Subtract the current weight from the starting weight to get the amount lost, then divide by the starting weight and multiply by 100. The same arithmetic works in reverse if the current weight is higher than the starting one; the result then shows a percentage gained instead of lost.
| Term | Meaning |
|---|---|
| Starting weight | The earlier weigh-in, used as the base the percentage is calculated against. |
| Current weight | The more recent weigh-in, compared back to the starting figure. |
| Percentage change | The difference between the two weights, expressed as a share of the starting weight rather than as a raw amount. |
The inputs explained
| Field | What to enter |
|---|---|
| Starting weight (kg) | The earlier weight. Any consistent unit works, kilograms or pounds, since the result is a percentage either way. |
| Current weight (kg) | The more recent weight, in the same unit as the starting weight. |
When to use it
Comparing progress between two people
A 5 kg loss means something different for someone starting at 60 kg than for someone starting at 120 kg. The percentage figure puts both changes on the same scale.
Reading a health report or study
Clinical weight-loss studies typically report results as a percentage of starting body weight rather than as raw kilograms, because it is the figure that transfers across different body sizes.
Checking a change over time without over-interpreting it
A single percentage figure describes what has happened, not why, and not whether the rate is a healthy one. Day-to-day weight also shifts with water and food in the gut, so figures close to zero are not necessarily meaningful.
Worked examples
Every figure in the tables below is produced by this page’s own calculator at build time, so the numbers and the tool always agree. Select any row to load that scenario.
What different amounts lost work out to from a 90 kg starting weight
The percentage figure for a range of amounts lost from the same starting weight.
| Current weight | Percentage lost | Amount lost |
|---|---|---|
| 88 kg | 2.22% | 2.00 (same unit as entered) |
| 85 kg | 5.56% | 5.00 (same unit as entered) |
| 81 kg | 10.00% | 9.00 (same unit as entered) |
| 76.5 kg | 15.00% | 13.50 (same unit as entered) |
| 72 kg | 20.00% | 18.00 (same unit as entered) |
| 63 kg | 30.00% | 27.00 (same unit as entered) |
Questions
Is a faster percentage loss better?
Not necessarily, and this calculator does not judge the rate either way. Sustainable loss is usually gradual; very fast percentage changes over a short period are more often water weight or measurement noise than fat loss.
Why use a percentage instead of just the kilograms lost?
A percentage accounts for starting body size, so it is the fairer way to compare progress between different people, or against published research that reports results the same way.
What if my current weight is higher than my starting weight?
The calculator reports a percentage gained instead of lost. The arithmetic is identical, just in the other direction.
Does this calculator tell me if my weight loss is healthy?
No. It only reports the arithmetic between two numbers you enter. Whether a given rate or amount is appropriate depends on individual circumstances that a doctor or dietitian is better placed to assess.
For the calories and time behind a change like this, see the weight change timeline calculator. For a daily calorie target, use the TDEE calculator.