Percentages come up everywhere: exam marks, discounts, GST, salary hikes, interest rates, election results, share prices. This Percentage Calculator handles the five questions people ask most often, each on its own tab:
- What is X% of Y? For example, 18% of ₹2,500
- X is what percent of Y? For example, 432 out of 500 marks
- Percentage increase from an old value to a new one, such as a salary hike
- Percentage decrease, such as a price drop
- Percentage difference between two values when neither is the “original”
How to use the percentage calculator
Pick the tab that matches your question, enter the two numbers and press Calculate. Each mode’s formula is below so you can check the answer or do it by hand in an exam.
1. What is X% of Y?
18% of 2,500 = 0.18 × 2,500 = 450.
Shortcut: X% of Y equals Y% of X. So 8% of 50 is the same as 50% of 8, which is 4. Swap the numbers when one order is easier.
2. X is what percent of Y?
You scored 432 out of 500: 432 ÷ 500 × 100 = 86.4%. To work out percentages across several subjects, use the Marks Percentage Calculator.
3. Percentage increase
Salary goes from ₹45,000 to ₹51,750 a month: (51,750 − 45,000) ÷ 45,000 × 100 = 15% hike.
4. Percentage decrease
A phone drops from ₹24,999 to ₹19,999: 5,000 ÷ 24,999 × 100 = 20.0% decrease.
5. Percentage difference
Use this when the two values are being compared as equals, with neither one the starting point, for example the prices of the same product in two shops:
₹480 vs ₹520: 40 ÷ 500 × 100 = 8%.
Percentage points vs percent
If a home-loan rate rises from 8% to 9%, it has gone up by 1 percentage point, but by 12.5 percent (1 ÷ 8 × 100). News reports and bank notices often mix these up. Percentage points describe the gap between two percentages. Percent describes relative change.
Why +X% then −X% doesn’t get you back
A ₹1,000 share that rises 20% goes to ₹1,200. If it then falls 20%, it ends at ₹960, not ₹1,000, because the fall is taken from the larger number. To recover a loss of L%, you need a gain of L ÷ (100 − L) × 100:
| Loss | Gain needed to break even |
|---|---|
| 10% | 11.1% |
| 20% | 25% |
| 25% | 33.3% |
| 50% | 100% |
Reverse percentages: finding the original
If a value after a percentage change is known, divide by the multiplier rather than subtracting the percentage:
- Price after 18% GST is ₹1,180, so the original is 1,180 ÷ 1.18 = ₹1,000 (not 1,180 − 18%).
- Salary after a 10% hike is ₹55,000, so the old salary was 55,000 ÷ 1.10 = ₹50,000.
Fraction–decimal–percent quick reference
| Fraction | Decimal | Percent |
|---|---|---|
| 1/2 | 0.5 | 50% |
| 1/3 | 0.333… | 33.33% |
| 1/4 | 0.25 | 25% |
| 1/5 | 0.2 | 20% |
| 1/6 | 0.1667 | 16.67% |
| 1/8 | 0.125 | 12.5% |
| 1/10 | 0.1 | 10% |
| 3/4 | 0.75 | 75% |
Competitive exams such as SSC, banking and CAT reward knowing these by heart. For example, 37.5% of 640 = 3/8 × 640 = 240.
Mental-maths tricks
- 10%: move the decimal point one place left. 1%: two places left.
- 5%: half of 10%. 15%: 10% + 5%. 25%: divide by 4.
- Any percentage: build it from 10%, 5% and 1%. For example, 17% of 600 = 60 + 30 + 12 = 102.
Frequently asked questions
How do I calculate the percentage of a number?
Multiply the number by the percentage and divide by 100. 15% of 840 = 840 × 15 ÷ 100 = 126.
How do I calculate a percentage from marks?
Divide marks obtained by total marks and multiply by 100. 456 out of 600 = 456 ÷ 600 × 100 = 76%.
What is the formula for percentage increase?
(New value − Old value) ÷ Old value × 100. From 80 to 92 is (92 − 80) ÷ 80 × 100 = 15%.
What is the difference between percentage change and percentage difference?
Percentage change measures change from an original value, so the direction matters. Percentage difference compares two values as equals, using their average as the base.
How do I find the original price before a percentage increase?
Divide the final value by (1 + percentage ÷ 100). If a price including 12% is ₹560, the original is 560 ÷ 1.12 = ₹500.