Percentages made simple
"Per cent" means "per hundred". A percentage shows a part of something as if the whole were 100. Percentages are everywhere: exam marks, discounts, GST, salary hikes, interest rates, election results and battery levels. This calculator answers the four most common percentage questions, and shows the formula for each, so you can check your work.
How to use the calculator
Pick the section that matches your question and type two numbers. Every answer updates instantly.
The four formulas
1. X% of Y
result = X ÷ 100 × Y
Example: 18% GST on ₹2,500 is 18 ÷ 100 × 2,500 = ₹450.
2. X is what percent of Y
percent = X ÷ Y × 100
Example: scoring 45 out of 60 is 45 ÷ 60 × 100 = 75%.
3. Percentage change
change % = (new − old) ÷ |old| × 100
Example: a salary rising from ₹40,000 to ₹46,000 is (46,000 − 40,000) ÷ 40,000 × 100 = +15%. A negative result means a decrease.
4. Increase or decrease by X%
increased = Y × (1 + X ÷ 100) decreased = Y × (1 − X ÷ 100)
Example: ₹1,200 increased by 15% is ₹1,380, and decreased by 15% is ₹1,020.
A common mistake
A rise of 10% followed by a fall of 10% does not bring you back to where you started. ₹100 + 10% = ₹110, but ₹110 − 10% = ₹99. That is because the second percentage is taken from a different, larger number. Likewise, to reverse a 20% discount you need a 25% increase, not 20%.
Percentage vs percentage points
If an interest rate goes from 8% to 10%, it rose by 2 percentage points, but by 25 percent (2 ÷ 8 × 100). News reports often mix these up, so check which one is meant.
Frequently asked questions
How do I find the original price before a discount?
Divide the sale price by (1 − discount ÷ 100). Our Discount Calculator does this for you.
How do I calculate percentage error in an experiment?
Use the Percentage Error Calculator.
Can I use negative numbers?
Yes. All four calculators accept negative and decimal values.