Percentage Calculator
Three different questions get called “percentage”. Pick the one you mean.
Read the maths behind this tool: Percentage Increase and Decrease: The Formula That Trips Everyone
The base changes
A 25% increase then a 25% decrease does not return you to the start: the decrease applies to the larger number.
Margin is not markup
Markup divides by cost; margin divides by price. Confusing them makes a quote look profitable when it is not.
How do I reverse a percentage change?
Divide by (1 + change). A 20% rise is undone by dividing by 1.2.
What is a percentage point?
The arithmetic difference between two percentages — 5% to 7% is 2 points, not 2%.