Percent change calculator: why −20% needs +25% to get back

80 to 100 is +25%. 100 back to 80 is only −20%. Same gap, different number — and that little difference explains a lot about risk.

Free tool · any two numbers · both directions · runs in your browser

How it works: percent change = (new − old) ÷ old × 100. The catch: the "old" number changes which way you go. 80 → 100 is +25%. 100 → 80 is −20%. Same gap, different percent.

Why up and down aren't mirror images

That small difference is why losses hurt more than they look. A drop of 20% needs a rise of 25% to get back; a drop of 50% needs 100%. The loss recovery calculator shows any number. It's also why traders measure moves from a fixed starting point — and why "it's only down 10%" can mean a lot.

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