The three formulas
- X% of Y = X × Y ÷ 100
- X as a percentage of Y = X ÷ Y × 100
- Percentage change from X to Y = (Y − X) ÷ X × 100; a positive answer is an increase, a negative one a decrease.
Everyday examples
| Question | Working | Answer |
|---|---|---|
| 10% increment on a Rs 80,000 salary | 80,000 × 10 ÷ 100 | Rs 8,000 (new salary 88,000) |
| 935 marks out of 1,100 | 935 ÷ 1,100 × 100 | 85% |
| Flour bag from Rs 250 to Rs 300 | 50 ÷ 250 × 100 | 20% rise |
| Back from Rs 300 to Rs 250 | −50 ÷ 300 × 100 | -16.67% |
The last two rows show that a rise and a fall of the same amount are not the same percentage, because the base changes. For shop sales, use the discount calculator.
Frequently asked questions
How do I calculate a percentage of a number?
Multiply the number by the percentage and divide by 100. For a 10% increment on a Rs 80,000 salary: 80,000 × 10 ÷ 100 = Rs 8,000, so the new salary is Rs 88,000.
How do I work out my marks percentage?
Divide the marks you obtained by the total marks and multiply by 100. 935 out of 1,100 is 935 ÷ 1,100 × 100 = 85%.
How do I calculate a percentage increase?
Take the new value minus the old value, divide by the old value and multiply by 100. If a price goes from Rs 250 to Rs 300, the rise is 50 ÷ 250 × 100 = 20%.
Why is a 20% rise followed by a 20% fall not back to the start?
Each percentage is taken of a different base. Rs 250 up 20% is Rs 300; Rs 300 down 20% is Rs 240. Going from 300 back to 250 is only a 16.67% fall.
What is the difference between percent and percentage points?
If a rate goes from 10% to 12%, it has risen by 2 percentage points but by 20 percent (2 ÷ 10 × 100). News reports on interest rates and inflation usually mean percentage points.
Related calculators
- Discount calculatorFind the sale price after a discount and how much you save, including “flat 50% + extra 20%” sales and optional GST added after the discount.
- Salary tax calculatorCalculate your monthly income tax and take-home salary under the 2026-27 budget, and see how much you save compared with 2025-26.
- Age calculatorFind your exact age in years, months and days from your date of birth, your age in total days, and the days left to your next birthday.
Sources
- Standard definition: per cent means “per hundred”, so X% of Y = X × Y ÷ 100. No official rate is involved.
This calculator gives an estimate for guidance. It is not official advice. Rates and rules change, so confirm important decisions with the relevant authority or a qualified professional. See how we calculate, or report a mistake.