Percentage Calculator
Solve every common percentage problem: X% of Y, what percent one number is of another, the whole from a part and a percentage, and percentage change.
What is the Percentage Calculator?
A percentage expresses a number as a fraction of 100. It is used for marks, discounts, interest, taxes, growth and much more.
How does it work?
Pick the question you want to answer and enter the two numbers. The calculator applies the matching formula instantly.
Formula
X% of Y = X ÷ 100 × Y
X as % of Y = X ÷ Y × 100
Whole = X × 100 ÷ Y
Change % = (Y − X) ÷ |X| × 100
Example
15% of 2,000 is 300. 45 out of 60 is 75%. If 30 is 20% of a number, the number is 150.
Everyday percentage problems
| Question | How to work it out | Example |
|---|
| What is 18% of ₹2,500? | 2,500 × 18 ÷ 100 | ₹450 |
| What percent is 42 of 60? | 42 ÷ 60 × 100 | 70% |
| ₹360 is 15% of what? | 360 × 100 ÷ 15 | ₹2,400 |
| From ₹40,000 to ₹46,000 is what change? | (46,000 − 40,000) ÷ 40,000 × 100 | 15% increase |
| ₹1,200 after a 25% discount | 1,200 × (1 − 0.25) | ₹900 |
Mental maths shortcuts
- 10% is the number divided by 10; 5% is half of that; 1% is the number divided by 100.
- Build other percentages from these: 15% = 10% + 5%; 18% = 20% − 2%.
- X% of Y equals Y% of X: 4% of 75 is the same as 75% of 4, which is 3.
- Doubling a percentage doubles the result: if 12% of a bill is ₹300, then 24% is ₹600.
Mistakes to avoid
Percentage changes are not symmetric. A 20% fall followed by a 20% rise does not get you back: ₹100 falls to ₹80, and 20% of ₹80 brings it only to ₹96. After a 50% loss, you need a 100% gain to recover.
Successive discounts multiply rather than add. “20% off plus an extra 10%” is 1 − (0.8 × 0.9) = 28% off, not 30%.
Percentage points are not percentages. A loan rate rising from 8% to 9% is an increase of 1 percentage point, but 12.5% in relative terms.
Always divide by the original value when calculating change. Dividing by the new value gives a different, usually wrong, answer.
Percentages in Indian contexts
- Marks: divide marks obtained by maximum marks and multiply by 100.
- GST: multiply the price before tax by the GST rate; to remove GST from an inclusive price, divide by (1 + rate) rather than subtracting a percentage of the total.
- Salary hikes and interest rates are quoted as percentages of the earlier amount or the principal.
Frequently asked questions
How do I calculate percentage of marks?
Divide marks obtained by total marks and multiply by 100. For example, 450 out of 500 is 90%. The Marks Percentage Calculator handles multiple subjects.
Is X% of Y the same as Y% of X?
Yes. 8% of 50 equals 50% of 8 — both are 4 — which can make mental math easier.
How do I calculate a percentage on a phone calculator?
Multiply by the percentage and divide by 100, for example 2,500 × 18 ÷ 100. Many phone calculators also have a % key, but it behaves differently between models, so the explicit method is safer.
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