Percentage formulas
X% of Y = X ÷ 100 × Y
X is what % of Y = X ÷ Y × 100
% change from X to Y = (Y − X) ÷ X × 100
Increase Y by X% = Y × (1 + X ÷ 100)
Decrease Y by X% = Y × (1 − X ÷ 100)
Examples
- 15% of 2,400 = 0.15 × 2,400 = 360.
- 450 out of 1,800 = 450 ÷ 1,800 × 100 = 25%. This is how exam marks become a percentage.
- Salary from ₹50,000 to ₹62,000 = (62,000 − 50,000) ÷ 50,000 = a 24% hike.
- ₹1,200 plus 18% GST = 1,200 × 1.18 = ₹1,416.
Percentage vs percentage points
If an interest rate goes from 8% to 10%, it has risen by 2 percentage points but by 25 percent. News reports often mix the two up.
A common trap
A 20% fall followed by a 20% rise does not bring you back to where you started: 100 → 80 → 96. To recover a 20% loss you need a 25% gain.
Frequently asked questions
How do I calculate percentage of marks?
Divide marks obtained by total marks and multiply by 100. For 450 out of 600: 450 ÷ 600 × 100 = 75%. Use the second box above.
How do I calculate a salary hike percentage?
Subtract the old salary from the new one, divide by the old salary and multiply by 100. Use the "percentage change" box.
How do I reverse a percentage increase?
Divide by (1 + rate/100), not multiply by (1 − rate/100). A price of ₹1,180 including 18% GST was ₹1,180 ÷ 1.18 = ₹1,000 before tax.
Results are for general information. Check important dates and figures against official sources.
Discount Calculator
GST Calculator
Profit Margin Calculator
Revenue Growth Calculator
Age Calculator
Date Difference Calculator