% Percentage Calculator
Percentages are just fractions of a hundred, but the wording trips people up: β20% offβ, βwhat percent is 30 of 200?β, βprices rose 15%β. The three tools below cover the three questions everyone actually asks.
Remember the golden rule for change: always divide by the original (starting) number, not the new one.
How to use this calculator
Pick the card that matches your question: a percent of a number, what percent one number is of another, or percent change. Fill in the two fields on that card for an instant answer.
- Choose the right card: 'What is X% of Y?', 'X is what percent of Y?', or 'Percent change from X to Y'.
- Type the two values into the card's fields, such as the Percentage and the Of number.
- Press Calculate to see the answer highlighted at the top of the card.
- Change the values and calculate again to compare discounts, tips or price changes side by side.
Frequently asked questions
What does this percentage calculator do?
The page handles three jobs, each as its own card: finding X percent of Y, finding what percent X is of Y, and finding the percent change from an original value to a new value. Fields are labeled plainly, such as Percentage, Of number, Original value and New value.
What formulas does it use?
The 'percent of' card multiplies X/100 by Y; the 'what percent' card divides X by Y and multiplies by 100; the change card divides the difference by the original value and multiplies by 100.
Can you show a worked example?
On the change card, enter an original value of 80 and a new value of 100: (100 - 80) / 80 = 0.25, so the answer is a 25% increase.
Any practical tip for percentage problems?
For change problems always compare against the original (starting) number, not the new one. Dividing by the wrong base is the classic percentage mistake, and it quietly makes every discount look bigger than it is.