Three formulas cover almost everything
Most percentage questions in daily life, from discounts and GST to marks, salary hikes and investment returns, come down to one of three calculations. Choose the question at the top and the calculator applies the right formula and shows it.
X% of Y = X ÷ 100 × Y
X is what % of Y = X ÷ Y × 100
% change X → Y = (Y − X) ÷ X × 100Worked example
Everyday uses
| Question | Mode | Example |
|---|---|---|
| How much is 12% interest on ₹2 lakh? | X% of Y | ₹24,000 |
| I scored 432 out of 500. What percentage? | X is what % of Y | 86.4% |
| My salary went from ₹60,000 to ₹69,000. What was the hike? | % change | 15% |
| Petrol went from ₹96 to ₹104. How much more? | % change | 8.33% |
The reverse-percentage trap
If a price after an 18% increase is ₹45,000, the original was not ₹45,000 minus 18%. You have to divide: ₹45,000 ÷ 1.18 = ₹38,135.59. The same applies when removing GST from an inclusive price. In this example, 45,000 ÷ (1 + 18%) = 38,135.59.
Also remember that a percentage increase and the same percentage decrease don't cancel out: a 50% fall followed by a 50% rise leaves you at 75% of where you started. That's why investment losses need bigger percentage gains to recover.
For money-specific versions, see the GST, discount and profit margin calculators.
Percentages in money decisions
Percentages hide surprises. A fund that falls 20% needs a 25% gain to recover. A salary raise of 10% taxed at 30% adds 7% to take-home pay. A loan at 1% a month is about 12.7% a year once compounded. Whenever a percentage appears in a money decision, ask: percentage of what, and over what period?
Frequently asked questions
How do I calculate percentage of marks?
Divide marks obtained by total marks and multiply by 100. 432 out of 500 = 86.4%.
How do I add a percentage to a number?
Multiply by (1 + percentage ÷ 100). ₹50,000 + 10% = ₹55,000.
What's the difference between percentage and percentage points?
If a rate moves from 6% to 8%, it rose by 2 percentage points, which is a 33% increase in the rate.