How to Calculate Percentage: Formula, Examples & Free Calculator
Percentages show up everywhere in business: discounts, GST, profit, commission, salary hikes and growth figures. The good news is that every percentage problem uses the same idea. A percentage is simply a number out of 100. So 15% means 15 out of every 100.
Want the answer without the maths? Use our free percentage calculator. Read on if you want to understand how it works.
The three basic percentage formulas
| What you want | Formula | Example |
|---|---|---|
| X% of a number | number × X ÷ 100 | 15% of 2,000 = 2,000 × 15 ÷ 100 = 300 |
| What % is A of B? | A ÷ B × 100 | 300 is what % of 2,000? 300 ÷ 2,000 × 100 = 15% |
| Percentage change | (new − old) ÷ old × 100 | 800 to 1,000 = 200 ÷ 800 × 100 = +25% |
Example 1: Find X% of a number
A customer pays a 30% advance on an order of ₹45,000. Advance = 45,000 × 30 ÷ 100 = ₹13,500. The balance is ₹31,500.
Shortcut: to find 10%, move the decimal point one place left (10% of 45,000 is 4,500). Then multiply: 30% is three times 10%, so 3 × 4,500 = 13,500.
Example 2: What percentage is one number of another?
You received 18 orders out of 240 enquiries. Conversion rate = 18 ÷ 240 × 100 = 7.5%.
Example 3: Percentage increase or decrease
Your sales were ₹80,000 last month and ₹92,000 this month. Change = (92,000 − 80,000) ÷ 80,000 × 100 = 15% increase. If sales had fallen from 92,000 to 80,000 the change would be (80,000 − 92,000) ÷ 92,000 × 100 = −13.04%. Notice the two answers differ, because the starting value is different each time. Always divide by the old value. See percentage increase and decrease for more.
Example 4: Add or subtract a percentage
- Add 10%: multiply by 1.10. ₹1,000 becomes ₹1,100.
- Subtract 10%: multiply by 0.90. ₹1,000 becomes ₹900.
- Add 18% GST: multiply by 1.18. ₹10,000 becomes ₹11,800. More in how to calculate GST.
Common mistakes to avoid
- Adding a percentage and removing the same percentage does not return the original. ₹100 + 10% = ₹110, but ₹110 − 10% = ₹99.
- Two discounts do not add up. 20% off and then 10% off is 28% off in total, not 30%. See how to calculate a discount.
- Percentage points are not percent. If a rate moves from 5% to 8%, it rose by 3 percentage points, which is a 60% relative increase.
Frequently asked questions
How do I calculate 20% of a number quickly?
Divide by 10 to get 10%, then double it. For 20% of 750: 75 × 2 = 150.
How do I turn a fraction into a percentage?
Divide the top number by the bottom and multiply by 100. For 3/8: 3 ÷ 8 = 0.375, so 37.5%.
How do I find the total when I know a percentage?
If 25% of a number is 500, the number is 500 ÷ 25 × 100 = 2,000.
Try all of these instantly in our free percentage and discount calculator.