What is the formula for percentage decrease?

Percentage decrease = ((Old Value – New Value) ÷ Old Value) × 100. If something drops from 800 to 600, the decrease is ((800–600)÷800)×100 = 25%.

Can I use this calculator for exam marks or GST calculations?

Yes! Our percentage calculator works for any scenario — exam scores, GST/tax calculations, discounts, profit/loss, salary hikes, and more. Just enter your numbers and get instant results.

Percentage Calculator – Calculate Percentages Online

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

To find X% of Y, multiply Y by X and divide by 100. For example, 20% of 500 = (500 × 20) ÷ 100 = 100. Use the 'Percent of a Number' tab in our calculator for instant results.

Q: How do I calculate percentage increase?

Percentage increase = ((New Value – Old Value) ÷ Old Value) × 100. For example, if a price goes from ₹200 to ₹250, the increase is ((250–200)÷200)×100 = 25%.

Q: How do I find what percent one number is of another?

Divide the part by the whole and multiply by 100. For example, 30 is what percent of 150? (30÷150)×100 = 20%. Use the 'X is What % of Y' tab in our tool.

🔢 Calculate Percentage

Percentage (%)

of Number

Result

—

Value (X)

Total (Y)

Result

—

Original Value

New Value

Result

—

Find the original number when you know a value is X% of it.

Known Value

Is What % of Original?

Original Number

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📋 How to Use This Calculator

Choose a calculation type by clicking one of the four tabs above (e.g., "% of a Number").
Enter your values in the input fields provided for that tab.
Click the Calculate button — your result appears instantly below the inputs.
Check the formula shown under the result to understand how it was calculated.
Use Clear to reset all fields and start a new calculation anytime.

ℹ️ About This Percentage Calculator

Our free percentage calculator is designed to handle all your everyday percent-related calculations quickly and accurately. Whether you need to calculate a percentage of a number (like finding 18% GST on a bill), figure out what percentage one number is of another (such as your exam score out of total marks), or determine the percentage increase or decrease between two values (like a salary hike or a product discount), this tool covers it all.

The fourth mode lets you reverse-engineer the original number when you know a value is a certain percentage of it — useful for working out pre-discount prices or pre-tax amounts. Every calculation displays a clear formula so you can verify and learn the math behind it. This percentage increase calculator and all its modes are 100% free, work entirely in your browser, and require no sign-up. Perfect for students, shoppers, business owners, and anyone who works with numbers daily.

❓ Frequently Asked Questions

How do I calculate a percentage of a number? +

To find X% of Y, use the formula: Result = (X ÷ 100) × Y. For example, 20% of 500 = (20 ÷ 100) × 500 = 100. Just enter the percentage and the number in the "% of a Number" tab and click Calculate.

How do I calculate percentage increase? +

Percentage increase = ((New Value – Old Value) ÷ Old Value) × 100. For example, if a price rises from ₹200 to ₹250, the increase = ((250 – 200) ÷ 200) × 100 = 25%. Use the "% Increase / Decrease" tab in our calculator.

How do I find what percent one number is of another? +

Divide the part by the whole, then multiply by 100: (Part ÷ Whole) × 100. Example: 30 is what percent of 150? = (30 ÷ 150) × 100 = 20%. Use the "X is What % of Y?" tab above.

Can I calculate the original price before a discount? +

Yes! Use the "Find Original Number" tab. If a product costs ₹480 after a 20% discount, enter 480 as the Known Value and 80 as the percentage (since 80% of original = discounted price). The result will be ₹600 — the original price.

Is this calculator useful for GST and tax calculations? +

Absolutely! To find 18% GST on ₹1,000, use "% of a Number": enter 18% of 1000 = ₹180 GST. To find a price before GST was added, use "Find Original Number": enter the GST-inclusive amount and the GST percentage to reverse-calculate the base price.