Percentage Calculator: how to use it

Percentages come up in shopping, exam results, salary changes, interest and business reports, and it is easy to use the wrong formula under pressure. This calculator offers the three questions people ask most often, and shows the working so you can check it.

Pick the question that matches your situation, type two numbers and press Calculate. Everything is computed instantly in your browser.

How to use the Percentage Calculator

1. Choose a Calculation: What is X% of Y?, X is what percent of Y?, or Percentage change from X to Y.
2. Enter the First value / percentage and the Second value. The labels change to match the question you picked.
3. Press Calculate and read the result and the formula beneath it.
4. Press Reset to try another calculation.

Tips for better results

• Discounts: to find the sale price of a Rs 2,500 item at 18% off, work out 18% of 2,500 (450) and subtract it, giving Rs 2,050.
• Marks: 45 out of 60 is what percent? Use the second option: 45 / 60 x 100 = 75%.
• Growth: a rise from 60 to 75 is a 25% increase, because (75 - 60) / 60 x 100 = 25.
• A percentage rise followed by the same percentage fall does not return you to the start: +20% then -20% leaves you 4% lower.

The three formulas

X% of Y = X / 100 x Y. X as a percent of Y = X / Y x 100. Percentage change = (new - old) / old x 100. A negative answer means a decrease. The percentage change from zero is undefined because you cannot divide by zero, so the tool asks you for a non-zero starting value.

Frequently asked questions

Why is percentage change not the same as percentage points?

Going from 10% to 15% is a rise of 5 percentage points but a 50% relative increase.

How many decimals does it show?

Up to four decimal places, with trailing zeros removed.

Can I use negative numbers?

Yes for the first two options where it makes sense, but percentage change needs a non-zero starting value.

Open the Percentage Calculator →

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