VSThiran

Students & Education

Free Percentage Calculator

Five percentage calculations in one place, with the answer explained in plain English.

Free to useNo sign-up requiredNo watermarkRuns in your browser

Last reviewed: 30 September 2026 by Vishal Senthilkumar

This free percentage calculator answers the five percentage questions that actually come up: what is X% of Y, what percentage one number is of another, how much something went up, how much it went down, and how far apart two values are. Pick the mode, type two numbers, and the answer appears as you type.

Every result comes with a short explanation of what it means, because a percentage on its own is easy to misread. The percentage increase and percentage difference modes in particular are often confused, and the tool tells you which one you are looking at.

How this tool works

  1. Choose the calculation you need

    The five tabs cover "What is X% of Y", "X is what % of Y", percentage increase, percentage decrease and percentage difference. Switching tabs loads a worked example so you can see the shape of the answer straight away.

  2. Enter your two numbers

    Decimals are fine, and so are negative numbers. The field labels change with the mode so it is always clear which number goes where.

  3. Read the result and the explanation

    The headline figure is the answer. Below it, the breakdown shows the absolute change, the direction and a few related figures, so you can sanity-check the number before using it.

  4. Copy it

    The copy button puts the whole calculation on your clipboard as a sentence, which is handy for pasting into a message, an email or a spreadsheet note.

How it works

A percentage is just a fraction with 100 on the bottom. "20%" means twenty parts out of a hundred, or 0.2 as a decimal. Every calculation on this page is that same idea rearranged to solve for a different unknown.

When you ask for a percentage of a number, the calculator converts the percentage to a decimal and multiplies. When you ask what percentage one number is of another, it divides the part by the whole and multiplies by 100. Percentage change divides the difference by the original value; percentage difference divides by the average of the two.

Negative starting values are handled by measuring change against the size of the original number rather than its sign, so going from -50 to -25 is reported as a 50% increase rather than a confusing negative result.

Zero is treated as a genuine error rather than quietly producing infinity. Nothing can be a percentage of zero, and percentage change from zero is undefined, so the calculator explains that instead of showing a meaningless figure.

Percentage increase, change and difference are not the same

These three get mixed up constantly, and using the wrong one is how people end up with numbers that do not survive scrutiny.

Percentage change has a direction. It measures movement from an original value to a new one, and it divides by the original. Going from 40 to 50 is a 25% increase, because the 10-unit rise is a quarter of the starting 40.

Percentage difference has no direction. It compares two values of equal standing and divides by their average, so swapping the two gives the same answer. The difference between 40 and 50 is 22.22%, because the 10-unit gap is measured against the average of 45.

  • Use percentage increase or decrease when one number came before the other - last month against this month, list price against sale price.
  • Use percentage difference when neither value is the baseline - two suppliers quoting for the same job, two readings from two instruments.
  • A 50% increase followed by a 50% decrease does not return you to where you started. 100 rises to 150, then falls to 75.

Where percentages come up in real life

  • Working out a mark on a test: 42 out of 60 becomes 70% using the "X is what % of Y" mode.
  • Checking a pay rise: an increase from 3,200 to 3,440 a month is a 7.5% rise.
  • Reading a statistic properly: a rise from 2% to 4% is a 2 percentage point increase, but a 100% increase. Both are true and they mean very different things.
  • Splitting a shared cost: if your share is 35% of a 480 bill, you owe 168.
  • Comparing quotes: two prices of 1,150 and 1,290 differ by about 11.5%.

Formula

Percentage of a number

result = value × (percent ÷ 100)

What percentage X is of Y

percent = (X ÷ Y) × 100

Percentage increase or decrease

change % = ((new − original) ÷ |original|) × 100

Dividing by the absolute value keeps negative starting points sensible.

Percentage difference

difference % = (|a − b| ÷ ((|a| + |b|) ÷ 2)) × 100

Symmetric: the order of the two values does not change the answer.

Worked examples

20% of 500

Convert 20% to 0.2 and multiply by 500 to get 100. The remaining 80% is 400.

100 is what percentage of 500?

Divide 100 by 500 to get 0.2, then multiply by 100 for 20%. The other 400 makes up the remaining 80%.

A price rising from 100 to 125

The 25-unit rise divided by the original 100 is 0.25, so a 25% increase.

A price falling from 125 to 100

The same 25-unit gap is now measured against 125, giving a 20% decrease. This is why a rise and the fall that undoes it are different percentages.

The difference between 40 and 50

10 divided by the average of 45 gives 22.22%. Compare that with the 25% increase from 40 to 50 - the same two numbers, two different questions.

A salary rising from AED 10,000 to AED 11,200 (salary increase percentage)

The percentage increase mode applies here directly: (11,200 - 10,000) / 10,000 = 0.12, so a 12% raise. The most common mistake is dividing by the new salary (11,200) instead of the old one, which understates the real percentage.

Frequently asked questions

Is this percentage calculator free?

Yes. Every calculator on VSThiran is free to use, with no sign-up, no usage limit and no watermark on anything you copy or download.

How do I calculate a salary increase percentage?

(new salary - old salary) / old salary x 100. AED 10,000 to AED 11,200 is (1,200 / 10,000) x 100 = 12%. Use the percentage increase mode above with your old salary as the first number and your new salary as the second.

How do I calculate what percentage one number is of another?

Divide the part by the whole and multiply by 100. For 42 out of 60: 42 ÷ 60 = 0.7, and 0.7 × 100 = 70%. The "X is what % of Y" mode does this for you.

What is the difference between percentage change and percentage points?

Percentage points describe the gap between two percentages. Going from 2% to 4% is a rise of 2 percentage points, and also a 100% increase. News reports often blur the two, which makes small changes sound dramatic.

Why does a 50% increase then a 50% decrease not get me back to the start?

Because the second percentage is applied to a bigger number. 100 plus 50% is 150; 150 minus 50% is 75. Each percentage is measured against whatever the value is at that moment.

Can I use negative numbers?

Yes. Percentage change is measured against the size of the original value, so a move from -50 to -25 is reported as a 50% increase, which is the intuitive reading.

How do I add or remove a percentage from a price?

To add 15%, multiply by 1.15. To remove 15% from a total that already includes it, divide by 1.15 rather than multiplying by 0.85 - those give different answers.