How the percentage calculator works
"Per cent" means "out of a hundred", so 15% simply means 15 out of every 100. This calculator handles the three percentage questions that come up most often in shopping, exams, business and finance. Choose a mode at the top, enter two numbers, and the result updates as you type. You also see the answers to the other two questions for the same numbers, plus a table of common percentages.
The three formulas in plain words
X% of Y = X ÷ 100 × Y X is what % of Y = X ÷ Y × 100 % change from X to Y = (Y − X) ÷ X × 100
Worked examples
- X% of Y: a 15% tip on a ₹2,000 bill is 15 ÷ 100 × 2,000 = ₹300.
- X is what % of Y: scoring 45 marks out of 150 is 45 ÷ 150 × 100 = 30%.
- Percentage change: a price rising from ₹80 to ₹100 is (100 − 80) ÷ 80 × 100 = 25% increase. Falling from ₹100 back to ₹80 is a 20% decrease, because the starting point is now 100.
Everyday uses
- Discounts: a 30% discount on ₹1,500 saves ₹450, so you pay ₹1,050. The "Subtracted" column in the table shows discounted prices at a glance.
- Markups and taxes: the "Added" column shows a value plus a percentage, useful for adding a margin or a tax.
- Marks and results: divide marks scored by maximum marks and multiply by 100.
- Salary hikes: use percentage change to compare your old and new salary.
- Investments: percentage change shows the gain or loss on a share or fund.
Common mistakes to avoid
Percentage changes are not symmetrical: a 50% fall followed by a 50% rise leaves you 25% lower than where you started. Also, "percentage points" are different from "percent": a rate moving from 8% to 10% is a rise of 2 percentage points, but a 25% increase in the rate itself. Finally, a percentage of zero is undefined, so the calculator warns you instead of showing a meaningless number.
Frequently asked questions
How do I calculate a percentage of a number?
Divide the percentage by 100 and multiply by the number. For 20% of 750: 20 ÷ 100 × 750 = 150.
How do I find what percent one number is of another?
Divide the part by the whole and multiply by 100. 30 out of 120 is 30 ÷ 120 × 100 = 25%.
How do I calculate percentage increase or decrease?
Subtract the old value from the new value, divide by the old value and multiply by 100. A positive answer is an increase; a negative answer is a decrease.
How do I calculate a discount?
Multiply the price by the discount percentage and divide by 100 to get the saving, then subtract it from the price. A 25% discount on ₹2,000 saves ₹500, so you pay ₹1,500.
What is the difference between percent and percentage points?
Percentage points measure the simple difference between two percentages (8% to 10% is +2 points). Percent change measures the relative change (8% to 10% is a 25% increase).