Weight Loss Percentage Calculator
Compare a starting weight with a current weight, calculate the percentage lost or gained, and measure progress toward an optional goal. Dates add an average weekly rate and an arithmetic goal-date projection.
Weight change is not the same as fat change. Hydration, food, medication, illness, muscle and measurement timing can move the scale. This calculator reports arithmetic, not a recommended pace or medical target.
Weight loss percentage formula
Weight loss % = (starting weight − current weight) ÷ starting weight × 100
If current weight is higher, the calculator labels the result as a gain instead of hiding it. Goal progress uses the distance traveled in the goal’s direction divided by the total distance from the starting weight to the goal. Displayed progress is limited to 0%–100%, while the explanation reports whether the measurement moved away from or passed the goal.
Average weekly change equals total change divided by elapsed days and multiplied by seven. A projected date is shown only when two valid dates are supplied, the goal has not been reached, and the measured trend is moving toward it.
Six checked examples
| Starting → current → goal | Change | Goal progress |
|---|---|---|
| 80 → 72 → 68 kg | 8 kg loss; 10.00% loss | 66.67%; 4 kg remaining |
| 200 → 180 → 170 lb | 20 lb loss; 10.00% loss | 66.67%; 10 lb remaining |
| 70 → 73 → 75 kg | 3 kg gain; 4.29% gain | 60.00%; 2 kg remaining |
| 90 → 90 → 80 kg | No change; 0.00% | 0.00%; 10 kg remaining |
| 60 → 55 → 55 kg | 5 kg loss; 8.33% loss | 100%; goal reached |
| 100 → 110 → 90 kg | 10 kg gain; 10.00% gain | 0%; moved away from goal |
How to use the result
- Use weights measured on the same scale under similar conditions when comparing a trend.
- Short-term changes often reflect water and stored carbohydrate, not only body tissue.
- The projected date assumes the historical average continues unchanged. Plateaus and day-to-day variation are normal.
- The calculator accepts values equivalent to 20–500 kg. It does not decide whether a goal or rate is appropriate.
- Seek qualified care for unexplained weight change or concerns involving pregnancy, childhood, medication, chronic illness or disordered eating.
Related calculators: Body Fat Calculator, Calorie Calculator, BMI Calculator and Percentage Calculator.
Questions
Can the percentage be negative?
The underlying signed percentage is positive for gain and negative for loss. For readability, the calculator displays the magnitude with a clear “loss,” “gain” or “no change” label.
Does switching units change the percentage?
No. Pounds and kilograms produce the same percentage because both weights use the same unit. Values are converted when you switch the selector.
Why is no goal date shown?
A projection needs a goal, two valid dates and a measured trend toward that goal. It is withheld for zero change, movement away from the goal, an already reached goal or missing dates.
Is this a body-fat-loss calculator?
No. Scale weight includes fat, muscle, water and other mass. Use the separate body-fat calculator for an estimate based on its stated assumptions.