Percentage Calculator

Percentages hide inside almost every money and study decision: discounts, tax, exam marks, tips, growth figures and interest. Our free percentage calculator covers the three questions people actually ask. First, what is X percent of Y, the classic discount and marks question. Second, what percentage is one number of another. Third, the percentage increase or decrease between two values, which is how you verify a pay rise, a price hike or a website traffic change. Clear results, no formulas to memorise.

Quick Answer: Choose a mode: find X% of a number, find what percentage one number is of another, or find the percentage increase or decrease between two numbers. Results are instant.

Free Online Tool

Three everyday modes: percent of a number, proportion, and change.

1) What is X% of Y?

Percentage (%)

Of number

2) X is what % of Y?

Part (X)

Whole (Y)

3) Percentage change

Old value

New value

Table of Contents

How to Use the Percentage Calculator

Pick the mode that matches your question from the three panels.
For 'X% of Y', enter the percentage and the base number, for example 20% of 150 for a discount amount.
For 'X is what % of Y', enter both numbers to get the share, like marks obtained out of total marks.
For change, enter the old value and the new value; the calculator shows the percentage increase or decrease with direction.
Use the result summary line in each panel to apply the answer, such as the final price after a discount.

Key Features

Three complete modes covering discounts, proportions and growth.
Worked result lines, not just a number: for discounts you see the amount saved and the price you actually pay.
Percentage change shows direction clearly, labelled increase or decrease.
Handles decimals and large numbers, from exam marks to company revenue.
Instant, in-browser calculations with no sign-up and no data stored.

Best Practices and Tips

To find a sale price quickly: calculate the discount amount with mode 1, then subtract; the panel does this for you.
A 50 percent loss needs a 100 percent gain to recover; percentage change is not symmetric, which mode 3 makes obvious.
For exam results, mode 2 with your obtained marks and total marks gives the percentage most report cards use.
Round only at the end: intermediate rounding is the most common cause of percentage answers that are a point or two off.

Common Mistakes to Avoid

Confusing percentage points with percent: a rise from 4% to 5% is one percentage point but a 25 percent relative increase.
Adding sequential discounts: 20% off then 10% off is not 30% off, because the second discount applies to the already reduced price.
Using the new value as the base for percentage change; change is always measured against the original value.

Frequently Asked Questions

How do I calculate a percentage of a number by hand?

Divide the percentage by 100 and multiply by the number. For 20% of 150: 20 ÷ 100 = 0.2, and 0.2 × 150 = 30. Mode 1 of the calculator does exactly this and also shows the remaining amount.

What is the formula for percentage change?

Subtract the old value from the new value, divide by the old value, and multiply by 100. A move from 80 to 100 is (100 − 80) ÷ 80 × 100 = 25% increase.

How do I work out my exam percentage?

Use mode 2: enter the marks you obtained as the first number and the total marks as the second. Obtaining 342 out of 400, for example, is 85.5%.

Can a percentage be more than 100?

Yes. A part can exceed the whole when it grows beyond the original reference, such as profits rising 150%, or a value doubling, which is a 100% increase to 200% of the original.

How do I reverse a percentage, like finding the price before VAT?

Divide the final amount by (1 + rate). For a price of 120 including 20% tax: 120 ÷ 1.2 = 100 before tax. Mode 1 can verify your result by calculating 20% of 100 and adding it back.