How to use the Percentage Calculator
- 1
Find the card that matches your question, from 1 to 5.
- 2
Type your numbers into its boxes. The sample values are there only to show how it works.
- 3
For card 4, choose Increase or Decrease first.
- 4
Read the answer in the blue box and the formula below it if you want to check the working.
The five calculations and the formula behind each
A percentage is just a fraction out of 100. Every card on this page rearranges that one idea, and the sample numbers already loaded in the calculator match the examples below.
| Question | Formula | Example |
|---|---|---|
| What is X% of Y? | (X ÷ 100) × Y | 15% of 2,400 = 360 |
| X is what % of Y? | (X ÷ Y) × 100 | 45 out of 60 = 75% |
| % change from old to new | ((New − Old) ÷ Old) × 100 | ₹25,000 to ₹28,000 = 12% increase |
| Increase Y by X% | Y × (1 + X ÷ 100) | 1,200 + 10% = 1,320 |
| Decrease Y by X% | Y × (1 − X ÷ 100) | 1,200 − 10% = 1,080 |
| Marks percentage | (Obtained ÷ Total) × 100 | 432 out of 500 = 86.4% |
The one people mix up most is percentage change. You always divide by the old value, the number you started from. If your rent goes from ₹25,000 to ₹28,000, the rise of ₹3,000 is divided by ₹25,000, giving 12%. Dividing by ₹28,000 instead would give 10.7%, which is the wrong answer.
Marks percentage, and converting CGPA
For board exams and most university results, add up the marks you scored and divide by the maximum marks. If you got 432 out of 500 across five subjects, your percentage is 432 ÷ 500 × 100 = 86.4%. If subjects carry different maximum marks, add all the obtained marks and all the maximum marks separately, then divide. Averaging the subject percentages gives a different, usually wrong, number when the maximums differ.
Grades are a separate matter. Under its old CCE scheme for Class 10, CBSE advised multiplying CGPA by 9.5 to get an indicative percentage, so a CGPA of 8.6 meant about 81.7%. Universities and boards often use their own conversion formulas, and some state clearly that no conversion applies. When a job or admission form asks for a percentage, use the formula printed on your marksheet or in your university's rules, and keep that document handy in case they ask how you arrived at the figure.
Three percentage traps worth knowing
These come up all the time with salary hikes, investment returns and shopping offers, so it pays to slow down and ask what the percentage is being taken of.
- A fall and an equal rise do not cancel. If a share drops 20% from ₹100 to ₹80 and then rises 20%, it reaches only ₹96. To get back to ₹100 from ₹80 it needs a 25% rise.
- Discounts do not add up. A sale with 20% off plus an extra 10% off is not 30% off. ₹1,000 becomes ₹800 and then ₹720, so the total discount is 28%.
- Percent and percentage points are different. If an FD rate goes from 7% to 7.5%, it has risen by 0.5 percentage points, but by 7.14% in relative terms (0.5 ÷ 7 × 100). News reports and bank ads sometimes use whichever sounds bigger.
Working backwards to the original number
Sometimes you know the final figure and the percentage, and you need the starting point. A shirt costs ₹1,080 after a 10% discount: what was the tag price? Do not add 10% of ₹1,080. Divide instead: ₹1,080 ÷ 0.90 = ₹1,200.
The same logic works for an increase. If your new salary is ₹66,000 a month after a 10% hike, your old salary was ₹66,000 ÷ 1.10 = ₹60,000. A quick check with card 4 confirms it: increase ₹60,000 by 10% and you get ₹66,000. Tax-inclusive prices follow this pattern too, which is how a GST amount is removed from a bill.
Shortcuts for doing it in your head
You will not always have a calculator open, and a few habits make mental percentages easy.
- 10% means moving the decimal one place left: 10% of ₹4,560 is ₹456. Half of that, ₹228, is 5%.
- Build other percentages from those: 15% is 10% plus 5%, so ₹684. 20% is double 10%.
- 1% is moving the decimal two places, which helps with interest rates and small changes.
- X% of Y equals Y% of X. 8% of 50 is hard to picture, but 50% of 8 is obviously 4.
Use the cards above when the numbers are awkward or when you need an exact answer to two decimal places, such as for a form, a bill or an assignment.
Frequently asked questions
How do I calculate a percentage of a number?
Divide the percentage by 100 and multiply by the number. For example, 15% of 2,400 is 0.15 × 2,400 = 360. Use card 1 above for any pair of numbers.
How do I calculate my marks percentage?
Divide the total marks you obtained by the maximum total marks and multiply by 100. 432 out of 500 gives 86.4%. Add up all subjects first rather than averaging each subject's percentage.
How do I calculate percentage increase?
Subtract the old value from the new value, divide by the old value and multiply by 100. Going from 25,000 to 28,000 is a 12% increase. If the result is negative, it is a decrease.
How do I convert CGPA to percentage?
There is no single formula. CBSE's old Class 10 rule was CGPA × 9.5, but many universities publish their own conversion. Always use the method stated on your marksheet or by your institution.
How do I add a percentage to a number?
Multiply the number by (1 + percentage ÷ 100). To add 10% to 1,200, multiply by 1.10 to get 1,320. Card 4 does this for both increases and decreases.
What is the difference between percent and percentage points?
Percentage points measure the simple gap between two percentages, while percent measures the relative change. A rate moving from 7% to 7.5% is up 0.5 percentage points, which is a 7.14% relative increase.
Last updated on November 9, 2026