What Is a Percentage Calculator?
A percentage calculator is a simple online math tool for solving problems involving percentages. It can tell you what a percentage of a number is, what percentage one value represents of another, how much a value increased or decreased, and what the final price becomes after a discount or percentage adjustment.
Percentages are everywhere: exam scores, discounts, business reports, budgets, sales growth, statistics, commissions, taxes, interest, sports records, and everyday comparisons. The arithmetic is usually straightforward, but entering the wrong number as the whole or mixing up percentage change with percentage difference can produce a misleading answer. This calculator separates the most common percentage questions into clear sections so you can choose the calculation that matches your problem.
For example, if a product costs 250 and you want to know 20% of it, the answer is 50. If you scored 50 points out of 200, your score is 25%. If a price moves from 100 to 125, the percentage increase is 25%. These are related calculations, but they use different formulas.
How to Use This Percentage Calculator
1. Find a percentage of a number
Use the first calculator when you already know the percentage and the number. Enter the percentage in the first box and the number in the second. The calculator multiplies the number by the percentage divided by 100.
Example: 15% of 400 = 60.
2. Find what percent one number is of another
Use the second calculator when you have a part and a whole. Enter the part as X and the total as Y. The result is calculated as X ÷ Y × 100.
Example: 45 out of 60 is 75%.
3. Find the whole from a known percentage
If you know that one value represents a particular percentage but you do not know the original total, use the third calculator. This is useful for reverse percentage problems, such as finding an original price when you know the discounted amount.
4. Calculate percentage increase or decrease
Enter the original value and the new value. The calculator compares the change with the original value. A positive result indicates an increase, while a negative result indicates a decrease.
5. Apply an increase or decrease
When you need to add or subtract a percentage from a starting value, use the fifth calculator. This is useful for price changes, markups, reductions, budget adjustments, and similar calculations.
6. Calculate percentage difference
Percentage difference is useful when there is no designated original or baseline value. It compares the absolute difference between two values with their average. This is different from percentage increase or decrease, where one value is explicitly the starting point.
7. Calculate a discount
Enter the original price and discount percentage to see the amount saved and the final price. For example, a 20% discount on a 100 price means a saving of 20 and a final price of 80.
Percentage Formulas
| Calculation | Formula | Example |
|---|---|---|
| Percentage of a number | (P ÷ 100) × X | 20% of 250 = 50 |
| What percent is X of Y? | (X ÷ Y) × 100 | 50 of 200 = 25% |
| Find the whole | (X × 100) ÷ P | 50 is 25% of 200 |
| Percentage change | ((New − Original) ÷ Original) × 100 | 100 → 125 = 25% |
| Percentage difference | |A − B| ÷ ((A + B) ÷ 2) × 100 | 80 and 100 = 22.2222% |
| Discount amount | Original × Discount ÷ 100 | 20% of 100 = 20 |
| Final price after discount | Original − Discount amount | 100 − 20 = 80 |
Percentage Examples
What is 30% of 500?
Convert 30% to 0.30 and multiply by 500: 0.30 × 500 = 150. Therefore, 30% of 500 is 150.
60 is what percent of 240?
Divide 60 by 240 and multiply by 100: (60 ÷ 240) × 100 = 25%. So 60 is 25% of 240.
A price rises from 80 to 100. What is the percentage increase?
The change is 20. Divide 20 by the original 80 and multiply by 100: (20 ÷ 80) × 100 = 25%. The price increased by 25%.
A 15% discount is applied to 200. What is the final price?
The discount is 15% of 200, which is 30. Subtract 30 from 200 and the final price is 170.
25 is 10% of what number?
Divide 25 by 10% expressed as 0.10: 25 ÷ 0.10 = 250. Therefore, 25 is 10% of 250.
Common Uses of Percentages
| Use case | How percentages help |
|---|---|
| Shopping | Calculate discounts, savings, sale prices, and price changes. |
| School and exams | Convert marks into percentages and compare results. |
| Business | Measure growth, margins, conversion rates, commissions, and changes. |
| Personal finance | Estimate percentage-based increases, reductions, budgets, and rates. |
| Statistics | Express parts of a dataset as proportions of the whole. |
| Sports | Compare winning rates, completion rates, shooting percentages, and other ratios. |
| Marketing | Calculate click-through rates, conversion rates, engagement rates, and changes over time. |
Common Percentage Mistakes
- Using the wrong baseline: Percentage increase or decrease normally uses the original value as the denominator.
- Confusing percentage points with percent change: Moving from 20% to 25% is a 5 percentage-point increase, but it is a 25% relative increase.
- Adding stacked discounts: A 20% discount followed by another 10% discount is not the same as a single 30% discount from the original price.
- Forgetting the percent sign: 20% means 20 ÷ 100, or 0.20.
- Dividing by zero: A percentage relationship cannot be calculated when the relevant denominator is zero.
- Rounding too early: Keep extra decimal places during intermediate steps and round the final result when appropriate.
Percentage Calculator for Students, Work and Everyday Math
This online percentage calculator is designed for quick everyday calculations without requiring a spreadsheet or manual formula. Students can use it for marks and grade percentages, shoppers can check sale prices, freelancers can estimate percentage changes in rates, and businesses can review simple growth or conversion figures.
Because all calculations happen directly in your browser, the tool is lightweight and does not need an account or external calculation service. Enter your values, check the result, and use the formula section when you want to understand how the answer was produced.
Frequently Asked Questions
What is 20% of 100?
20% of 100 is 20. Multiply 100 by 20 ÷ 100 to get 20.
How do I calculate a percentage?
To find what percentage one number is of another, divide the part by the whole and multiply by 100. Formula: (part ÷ whole) × 100.
How do I calculate percentage increase?
Subtract the original value from the new value, divide the result by the original value, and multiply by 100.
How do I calculate percentage decrease?
Subtract the new value from the original value, divide by the original value, and multiply by 100. The result represents the percentage decrease.
What is the difference between percentage change and percentage difference?
Percentage change uses a specific starting value as the baseline. Percentage difference compares two values using their average, so neither value is treated as the starting point.
How do I calculate a discount percentage?
Multiply the original price by the discount percentage divided by 100 to find the saving. Subtract that saving from the original price to find the final price.
Can percentages be greater than 100%?
Yes. A percentage can exceed 100% when the part is larger than the reference whole. For example, 150 is 150% of 100.
Can I calculate negative percentages?
Yes. Negative percentage values can represent reductions or changes in the opposite direction, depending on the calculation.