The percentage of body weight lost between a starting weight and a current weight — the metric many structured weight-loss programs use to track progress.
How it works
The difference between starting and current weight is divided by the starting weight, then converted to a percentage.
What this does not include
This does not include a daily calorie deficit calculation — for working forward from a weight-loss goal to a daily calorie target, use this site’s calorie deficit calculator instead.
How to use this calculator
- Enter your starting weight and current weight.
A worked example
Starting weight 200 lb, current weight 180 lb: amount lost = 20 lb, percent lost = 20 ÷ 200 × 100 = 10%.
Starting weight 150 lb, current weight 140 lb: percent lost = 6.67%.
What the variables mean
| Variable | Meaning |
|---|---|
| Starting weight | Weight at the beginning of the tracking period |
| Current weight | Weight now |
Edge cases worth knowing
Percent lost is relative to starting weight, not a fixed scale. The same 10 lb loss represents a bigger percentage for someone starting lighter than for someone starting heavier — which is why health guidelines often use percentage rather than raw pounds.
A starting weight of zero makes the percentage undefined — there’s no baseline to measure the loss against, so the calculator returns no result.
Frequently asked questions
Why use percentage instead of raw pounds or kilograms lost?
Percentage accounts for body size — losing 20 lb means something different for a 150 lb person than a 300 lb person, and percentage normalizes that comparison.
Why do some weight-loss programs specifically track percentage?
Many structured programs (including some clinical weight-loss guidelines) use percentage-based milestones, like “5% of starting weight,” as meaningful markers of health improvement.
Can this calculator show weight gain instead of loss?
The result would show as a negative percentage lost if current weight exceeds starting weight, though this tool is framed around the loss direction.
