Percentage calculations appear everywhere — from GST and discounts to investment returns and salary increments. Knowing the right formula for each scenario saves time and prevents costly mistakes. Here are the four most common percentage calculations and how to do them.
1. What is X% of Y?
Result = (X ÷ 100) × Y
Example: What is 18% of ₹5,000? = (18÷100) × 5,000 = ₹900 (this is your GST amount)
2. X is What Percent of Y?
Percentage = (X ÷ Y) × 100
Example: ₹750 is what percent of ₹5,000? = (750÷5,000) × 100 = 15%
3. Percentage Change (Increase or Decrease)
% Change = ((New Value − Old Value) ÷ Old Value) × 100
Example: Salary increased from ₹60,000 to ₹72,000. % increase = ((72,000−60,000) ÷ 60,000) × 100 = 20% increment
4. Adding or Removing Percentage
- To add X%: Final = Original × (1 + X/100). E.g., ₹10,000 + 18% GST = ₹10,000 × 1.18 = ₹11,800
- To remove X%: Base = Final ÷ (1 + X/100). E.g., MRP ₹11,800 − 18% GST = ₹11,800 ÷ 1.18 = ₹10,000
Common mistake: To remove 18% GST from ₹11,800, many people calculate 18% of ₹11,800 = ₹2,124 and subtract to get ₹9,676. This is wrong! The correct base price is ₹10,000. Always divide by (1+rate), never subtract a percentage of the final amount.
Real-Life Uses
| Scenario | Formula Used | Example |
|---|---|---|
| GST calculation | Add % or Remove % | Add 18% to base price |
| TDS on FD | X% of Y | 10% of ₹50,000 interest |
| Salary increment | % Change | Old vs new CTC |
| Discount calculation | X% of Y | 30% off MRP ₹2,000 |
| Investment return | % Change | Portfolio up ₹20K on ₹1L |
Use our Percentage Calculator — all four methods in one tool, instant results.