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Percentage Calculator

Percent of

Example: 15% of 200 = 30

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Increase by Percent

Example: 200 + 15% = 230

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Decrease by Percent

Example: 200 - 15% = 170

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How to use the Percentage Calculator?

The Percentage Calculator handles three types of percentage problems in one tool. Mode 1 answers 'What is X% of Y?' (e.g., what is 15% of 200 = 30). Mode 2 answers 'X is what percent of Y?' (e.g., 30 is 15% of 200). Mode 3 answers 'What is Y after increasing or decreasing by X%?' (e.g., 200 increased by 15% = 230, or 200 decreased by 15% = 170). Results update instantly as you type, with no need to press a button. All three modes cover the vast majority of percentage questions that come up in everyday life.

Percentages appear in nearly every domain of daily life: retail discounts and sale prices, tax calculations, interest rates, tip amounts, grade scores, statistical data, business profit margins, and investment returns. Understanding how to work with percentages quickly and accurately — in both directions — gives you a practical edge in financial decisions, shopping, and data interpretation. The ability to switch between 'finding a percent of a number' and 'finding what percent a number represents' is especially useful for comparisons.

The underlying formulas are straightforward: to find X% of Y, compute Y × (X/100). To find what percentage X is of Y, compute (X/Y) × 100. To increase Y by X%, compute Y × (1 + X/100); to decrease, compute Y × (1 − X/100). This calculator handles these operations so you can focus on the result. All calculations run locally in your browser — no data is sent to any server, and results are available offline.

How to Use the Percentage Calculator

  1. 1

    Select the calculation mode that matches your question: 'Percent of a Number,' 'What Percent Is X of Y,' or 'Increase/Decrease by Percent.'

  2. 2

    For Mode 1 (Percent of Number): enter the percentage value and the base number to find the resulting amount.

  3. 3

    For Mode 2 (What Percent): enter both numbers to find what percentage the first number is of the second.

  4. 4

    For Mode 3 (Increase/Decrease): enter the original number and the percentage, then toggle between increase and decrease.

  5. 5

    Results appear instantly as you type — there is no Calculate button to press.

  6. 6

    Click the copy icon to copy the result to your clipboard for use in other applications.

Frequently Asked Questions

How do I calculate a percentage of a number?
Formula: Result = Number × (Percentage divided by 100). Example: 15% of 200 = 200 × 0.15 = 30. Use Mode 1 in this calculator — enter 15 as the percentage and 200 as the number. The result is 30.
How do I find what percentage one number is of another?
Formula: Percentage = (Part divided by Whole) × 100. Example: what percent is 30 of 200? = (30 divided by 200) × 100 = 15%. Use Mode 2 — enter 30 and 200. The result is 15%.
How do I calculate a percentage increase?
Formula: New Value = Original × (1 + Percentage divided by 100). Example: 200 increased by 15% = 200 × 1.15 = 230. To find the percentage change between two numbers: ((New minus Old) divided by Old) × 100.
How do I calculate a sale price after a discount?
Subtract the discount percentage from 100%, then multiply by the original price. Example: $120 item at 30% off = 120 × 0.70 = $84. The discount amount is 120 × 0.30 = $36. This is Mode 3 (Decrease by Percent) in this calculator.
What is the difference between a percentage point and a percent change?
A percentage point is an absolute arithmetic difference between two percentages. A percent change is relative. Example: if an interest rate rises from 2% to 3%, that is 1 percentage point — but it is a 50% relative increase in the rate. The distinction is critical in finance, polling, and statistics.
How do I quickly calculate a tip percentage mentally?
Find 10% first by moving the decimal point one place left. Then adjust: 20% = double the 10% figure; 15% = the 10% figure plus half of it; 18% ≈ double the 10% figure minus a small amount. Example: 18% of $65 — 10% = $6.50, 20% = $13.00, 18% ≈ $11.70.
Can I calculate a tax-inclusive price?
Yes. Use Mode 1 to find the tax amount (e.g., 8% of $100 = $8), then add it to the original price ($108 total). Or use Mode 3 (Increase by Percent) to get the tax-inclusive price directly: $100 increased by 8% = $108.