Math Tool

Percentage Calculator

Q: How do I find a percentage of a number?

Use the "X% of Y" mode. Enter the percentage and the number. For example, 15% of 200 = 30. This is useful for tips, discounts, and tax calculations.

Q: How do I calculate percentage change between two numbers?

Use "% Change" mode. Enter the original and new values. The calculator shows percentage increase (positive) or decrease (negative) between the two values.

Q: How do I calculate a discount percentage?

Use "% Change" mode. Enter the original price and sale price. If original is $100 and sale is $75, the result shows -25%, meaning a 25% discount.

Multi-mode percentage calculations — find percentages, calculate changes, and reverse calculations

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What is X% of Y?

% of

How to Use This Percentage Calculator

This free percentage calculator handles four common percentage calculations that come up in everyday life, shopping, finance, and school. Simply select the mode you need and enter your numbers:

X% of Y — find a specific percentage of a number (e.g., 15% of 200 = 30). Great for calculating tips, discounts, and tax amounts.
% Change — calculate the percentage increase or decrease between two values (e.g., price went from $50 to $65 = 30% increase).
X is % of Y — find what proportion one number is of another (e.g., 30 is 15% of 200). Useful for grades, stats, and ratios.
Reverse — find the original value before a percentage was added (e.g., $115 after 15% tax → original was $100). Essential for removing tax or markup.

How This Percentage Calculator Works

Each mode uses a straightforward mathematical formula:

X% of Y = (X / 100) × Y
% Change = ((New - Original) / Original) × 100
X is % of Y = (X / Y) × 100
Reverse = Final / (1 + Percent / 100)

Results are calculated instantly in your browser with up to 4 decimal places of precision. All calculations happen client-side — your numbers are never sent to any server.

Examples

Calculating a Tip

Restaurant bill is $85 and you want to leave a 20% tip? Use "X% of Y" mode: enter 20 and 85 to get $17. Total with tip = $102.

Sale Discount

A jacket originally costs $150 and is now $112.50. Use "% Change" mode: from 150 to 112.50 shows a 25% decrease. That's your discount percentage!

Removing Tax from a Price

You paid $113 for an item that includes 13% HST. Use "Reverse" mode: enter 113 and 13 to find the pre-tax price was $100. The tax portion was $13.

Frequently Asked Questions

How do I find a percentage of a number?▼

Use the "X% of Y" mode. Enter the percentage you want to find and the number you're calculating it from. For example, to find 15% of 200, enter 15 and 200. The result (30) appears instantly.

How do I calculate percentage change between two numbers?▼

Use "% Change" mode. Enter the original value and the new value. The calculator shows whether it's an increase (positive %) or decrease (negative %), along with the exact percentage change.

What is reverse percentage calculation?▼

Reverse percentage finds the original value before a percentage was added. For example, if a price is $115 after adding 15% tax, the reverse calculation shows the original was $100. This is useful for removing tax, markup, or any added percentage from a final amount.

How do I calculate a discount percentage?▼

Use "% Change" mode. Enter the original price as the first value and the sale price as the second. If the original is $100 and the sale price is $75, the calculator shows -25% — meaning the discount is 25%.

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Last updated: February 2026

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