Percentage Calculator
Work out a percentage of a number, what percent one number is of another, and the percentage increase or decrease between two numbers.
Percentage change is measured against the starting number, so a 10% rise followed by a 10% fall leaves you 1% below where you began.
Percentage formulas
A percentage is a number out of 100. Three formulas cover almost every question:
| Question | Formula | Example |
|---|---|---|
| What is X% of Y? | X ÷ 100 × Y | 18% of ₹1,000 = ₹180 |
| X is what % of Y? | X ÷ Y × 100 | 450 out of 500 = 90% |
| % increase or decrease | (New − Old) ÷ Old × 100 | ₹50,000 → ₹54,000 = +8% |
How to calculate percentage of a number
Multiply the number by the percentage and divide by 100. 15% of ₹2,400 = 2,400 × 15 ÷ 100 = ₹360.
Quick way to work it out in your head
Find 10% by moving the decimal one place left, then build up. For 18% of ₹2,500: 10% is ₹250, 5% is ₹125 and 3% is ₹75, so 18% is ₹450. 1% is the number ÷ 100, and 50% is half.
How to calculate percentage of marks
Add the marks you scored in all subjects, divide by the total maximum marks and multiply by 100. Scoring 78, 85, 92, 66 and 89 out of 100 in five subjects is 410 out of 500, which is 82%.
- Different maximum marks per subject: add all scored marks and all maximum marks separately, then divide. Do not average the subject percentages.
- CGPA to percentage: on CBSE Class 10 marksheets from the CGPA system used until 2017, CBSE’s conversion is percentage = CGPA × 9.5, so 8.6 CGPA = 81.7%. Universities use their own formulas; use the one printed on your grade card.
How to calculate attendance percentage
Attendance % = classes attended ÷ classes held × 100. 50 of 80 classes is 62.5%. To reach 75%, you need 3 × classes held − 4 × classes attended more classes in a row: 3 × 80 − 4 × 50 = 40 more classes, which takes you to 90 out of 120.
How to calculate percentage increase
Subtract the old value from the new one, divide by the old value and multiply by 100. A salary rise from ₹50,000 to ₹54,000 a month is 4,000 ÷ 50,000 × 100 = 8%. Always divide by the starting value, not the new one.
How to calculate percentage decrease
Same formula: (old − new) ÷ old × 100. A phone price cut from ₹25,000 to ₹21,000 is 4,000 ÷ 25,000 × 100 = 16% off.
A fall and an equal rise do not cancel. ₹100 down 10% is ₹90; up 10% from there is ₹99, which is 1% below where it began. A 50% fall needs a 100% rise to get back.
How to find the original price before a discount
Divide the price you paid by (1 − discount ÷ 100). If you paid ₹1,600 after a 20% discount, the original price was 1,600 ÷ 0.8 = ₹2,000, not 1,600 + 20%. For a price including 18% GST, divide by 1.18: ₹1,180 ÷ 1.18 = ₹1,000.
Do two discounts add up?
No. 20% off and then a further 10% off is 0.8 × 0.9 = 0.72 of the price, which is 28% off, not 30%.
How to calculate profit percentage
Profit % = (selling price − cost price) ÷ cost price × 100. Buying at ₹800 and selling at ₹1,000 is a 25% profit on cost. Shops often quote margin instead, which divides by the selling price: the same sale is a 20% margin. A 25% markup is always a 20% margin.
How to calculate percentage in Excel
- X% of a number:
=A1*B1, with the percentage typed as 18% in B1. - What % one number is of another:
=A1/B1, formatted as a percentage. - Percentage change:
=(B1-A1)/A1, formatted as a percentage.
Percentage vs percentage points
A change from 8% to 9% is a rise of 1 percentage point, but a 12.5% increase in the rate itself. Interest rate news uses percentage points or basis points: RBI’s repo rate rise from 5.25% to 5.50% in October 2026 was 0.25 percentage points, or 25 basis points. On a home loan, that small-sounding change adds hundreds of rupees to the EMI.
When to use a different calculator
- Adding or removing GST? Use the GST Calculator.
- Working out a new salary after a hike? Use the Salary Hike Calculator.
- Growth over several years? Use the CAGR Calculator.