Why is % change based on the absolute value of A?

So a change from -10 to 10 is reported as a +200% change, not -200%. This is the standard convention when the starting value can be negative.

What if I divide by zero?

The calculator returns 0 rather than infinity when Y or A is zero — treat that as 'undefined'.

Three common percentage questions, one page. Pick a tab and type — results update live.

X (percent)

Y (of value)

25% of 200

50.00

X% of Y multiplies Y by X ÷ 100. Example: 25% of 200 = 50.

X is what % of Y divides X by Y and multiplies by 100. Example: 25 is 12.5% of 200.

% change from A to B is (B − A) ÷ |A| × 100. A positive result is an increase; a negative result is a decrease.