Choose a mode — percentage of a number, what percent X is of Y, or percentage increase/decrease — and get the result with the formula used.

How to Use the Percentage Calculator

Pick a mode first — percentage of a number, what-percent-of, or percentage change — since the three read similarly in plain English but need different fields filled in.

People say "percentage" and mean three different questions, constantly. What is 20% of 150? What percent of 150 is 30? How much did something change, in percent? Same word, three separate calculations — which is why this tool splits them into modes instead of pretending one formula covers it all.

X% of a number:        (percentage ÷ 100) × number
What percent is X of Y: (part ÷ whole) × 100
Percentage change:      ((new − original) ÷ original) × 100

20% of 150 is 30. 30 is 20% of 150. Going from 150 to 180 is a 20% increase. All three read like the same sentence rearranged, and that's exactly why they get mixed up.

The one mix-up worth actually flagging: percent versus percentage point. A rate moving from 10% to 12% is a 2 percentage point increase, but a 20% relative increase (2 ÷ 10 × 100) — reporting the second number as "12% up" overstates things by 6x. If the two figures you're comparing are already percentages themselves — two interest rates, two survey results — their plain difference is in points, not percent.

A 20% increase followed by a 20% decrease doesn't get you back to where you started. 100 up 20% is 120; 120 down 20% is 96, not 100 — the second calculation runs against the new, bigger number, not the original.