Calculate the percentage change between an original value and a new value. See whether it went up or down, and by how much.
Percentage change answers: “how big is the move from A to B, relative to A?”
Example: a price goes from 80 to 100. (100 − 80) ÷ 80 × 100 = +25% (increase). From 100 back to 80 is −20% (decrease). The two directions are not the same size — that is expected.
Percentage change is always relative to the original number and can be negative. Percentage difference is a different formula (usually the gap divided by the average of the two numbers) and is always positive. This tool does change, which is what people mean by “sales were up 12%”.
You cannot divide by zero. If the original value is 0, a percentage change is undefined (going from nothing to something is not a finite percent).
All math runs in your browser. Your numbers are never sent to any server and never stored.
((new − original) / original) × 100. A positive result is an increase. A negative result is a decrease. Example: 50 → 75 is +50%.
Each percent is relative to a different starting point. 20 is 20% of 100, but 25% of 80. The calculator is doing that on purpose.
No. Change uses the original value as the base and can be signed (+/−). Difference usually uses the average of the two numbers and is unsigned. Use change for growth rates.
Yes. Put the old price as Original and the sale price as New. A $40 item on sale for $30 is a 25% decrease.
Percentage change is undefined. The tool shows a dash instead of a fake number. Going from 0 to 10 is not “infinity percent” in any useful business sense.
Yes. Everything runs locally in your browser. Nothing is uploaded or stored.