Percentage Calculator
Instant percentage calculations for any scenario
A free multi-function percentage calculator covering the four most common percentage problems: finding X% of a number, determining what percent one number is of another, calculating percentage change (increase or decrease), and adding or removing a percentage such as GST or a discount. Results update in real time as you type.
What is X% of Y?
Formula: (X ÷ 100) × Y
X is what % of Y?
Formula: (X ÷ Y) × 100
Percentage Change (Increase / Decrease)
Formula: ((New − Old) ÷ Old) × 100
Add / Remove Percentage
Formula: 1000 + (18% × 1000) = 1180
What Is a Percentage?
A percentage is a way of expressing a number as a fraction of 100. The word "percent" comes from the Latin per centum, meaning "out of one hundred." Percentages are used everywhere — from test scores and discounts to tax rates, interest rates, and statistical data.
When you see "25%," it means 25 out of every 100. To convert a percentage to a decimal, divide by 100 (25% = 0.25). To convert a decimal to a percentage, multiply by 100 (0.25 = 25%).
How to Use This Calculator
- What is X% of Y? — Enter the percentage and the number. Use this for discounts, tips, tax amounts, and similar problems.
- X is what % of Y? — Enter both numbers to find what percentage the first is of the second. Useful for comparing scores or proportions.
- Percentage Change — Enter the old and new values to calculate the % increase or decrease between them.
- Add / Remove % — Enter a base amount, choose add or subtract, and enter a rate. Perfect for GST, VAT, discounts, and markups. Results update live.
Percentage Formulas
| Problem Type | Formula | Example |
|---|---|---|
| X% of Y | (X ÷ 100) × Y | 15% of 200 = 30 |
| X is what % of Y | (X ÷ Y) × 100 | 30 is 15% of 200 |
| Percentage Change | ((New − Old) ÷ Old) × 100 | 100 to 150 = +50% |
| Add % | Amount × (1 + Rate/100) | 1000 + 18% = 1180 |
| Remove % | Amount × (1 − Rate/100) | 1000 − 20% = 800 |
| Reverse % (original) | Final ÷ (1 + Rate/100) | 1180 ÷ 1.18 = 1000 |
Common Percentage Quick Reference
| Percentage | Fraction | Decimal | Of 1000 |
|---|---|---|---|
| 1% | 1/100 | 0.01 | 10 |
| 5% | 1/20 | 0.05 | 50 |
| 10% | 1/10 | 0.10 | 100 |
| 12% | 3/25 | 0.12 | 120 |
| 18% | 9/50 | 0.18 | 180 |
| 20% | 1/5 | 0.20 | 200 |
| 25% | 1/4 | 0.25 | 250 |
| 50% | 1/2 | 0.50 | 500 |
Worked Examples
Example 1 — Discount: A jacket costs ₹2,500 and is on sale at 30% off. Discount = 30% of 2500 = 750. Sale price = 2500 − 750 = ₹1,750.
Example 2 — GST: A product costs ₹850 before 18% GST. Tax = 18% of 850 = 153. Total = 850 + 153 = ₹1,003.
Example 3 — Percentage increase: Your salary increased from ₹40,000 to ₹46,000. Change = ((46000 − 40000) ÷ 40000) × 100 = 15% increase.
Example 4 — Test score: You scored 72 out of 90. Percentage = (72 ÷ 90) × 100 = 80%.
Example 5 — Reverse GST: A bill shows ₹1,180 including 18% GST. Original price = 1180 ÷ 1.18 = ₹1,000.
Tips and Shortcuts
- To find 10% of any number, move the decimal one place left (10% of 350 = 35).
- To find 5%, find 10% and halve it (5% of 350 = 17.5).
- To find 1%, move the decimal two places left (1% of 350 = 3.5).
- For GST calculations, use the Add % section — enter your base price and the GST rate.
- A negative percentage change means a decrease. Example: −25% means the value fell by a quarter.
- To check if a percentage answer is reasonable, estimate: 15% of 200 should be close to 30 (15 × 2).
Frequently Asked Questions
Multiply the number by X and divide by 100. Example: 15% of 200 = (15 × 200) ÷ 100 = 30. Or use the "What is X% of Y?" section above.
Subtract old value from new, divide by old value, multiply by 100. Example: from 100 to 150 = ((150−100)÷100)×100 = 50% increase. Use the Percentage Change section above.
18% of 1000 = 180. So the total with GST = ₹1180. Use the Add Percentage section above — enter 1000, select + add, and enter 18.
Use the percentage change formula: ((New - Old) / Old) × 100. A negative result indicates a decrease. Example: from 200 to 150 = ((150-200)/200) × 100 = −25%.
Divide 30 by 200 and multiply by 100: (30 / 200) × 100 = 15%. So 30 is 15% of 200. Use the "X is what % of Y?" section above.
To find the original price before a percentage was added, divide the final amount by (1 + Rate/100). For example, to reverse 18% GST from ₹1180: 1180 ÷ 1.18 = ₹1,000. Use the subtract option in the Add/Remove section and enter the GST-inclusive price.
Percentage Change = ((New Value − Old Value) ÷ Old Value) × 100. A positive result is an increase, a negative result is a decrease.