How to use the percentage calculator

1Choose a calculation: X% of Y, X is what % of Y, % change, % difference or Increase / decrease.
2Type the two numbers into the boxes. The result updates as you type.
3Read the answer and the formula with your numbers underneath. Press Copy result to copy it.

Four common questions

Input

15% of 240
45 is what % of 60
% change from 80 to 100
% difference between 80 and 100

Output

36
75%
+25% (increase)
22.2222%

A change from 100 back to 80 is −20%, not −25%: the percentage change is always measured from the starting value.

X percent of Y

"Percent" means "per hundred", so X% of Y is X ÷ 100 × Y. 15% of 240 = 0.15 × 240 = 36.

Percentages are reversible: X% of Y equals Y% of X. 8% of 50 is the same as 50% of 8, which is 4, a handy shortcut for mental arithmetic.

X is what percent of Y

Divide the part by the whole and multiply by 100: X ÷ Y × 100. 45 out of 60 is 45 ÷ 60 × 100 = 75%.

The whole (Y) can't be zero. If the part is bigger than the whole the answer is over 100%, which is correct: 90 is 150% of 60.

Percentage increase and decrease

Percentage change compares a new value with an old one:

% change = (New − Old) ÷ |Old| × 100

From 80 to 100 is +25%; from 100 to 80 is −20%. The two differ because each is measured from its own starting value. A 50% fall followed by a 50% rise leaves you at 75% of where you started.

Increase / decrease goes the other way: 240 increased by 15% is 240 × 1.15 = 276. To undo a percentage increase, divide rather than subtract: 276 ÷ 1.15 = 240.

Percentage difference vs percentage change

Use percentage change when one value clearly comes first (last year vs this year, old price vs new price). Use percentage difference when neither value is the reference, for example two shops' prices or two lab measurements:

% difference = |A − B| ÷ ((A + B) ÷ 2) × 100

It divides by the average of the two values, so swapping A and B gives the same answer. 80 and 100 differ by 20 ÷ 90 × 100 = 22.22%.

Don't confuse either with percentage points: a rate rising from 4% to 5% is a rise of 1 percentage point, but a 25% increase.

Percentage of marks

Choose X is what % of Y, enter the marks you scored as X and the maximum marks as Y. 432 out of 500 is 432 ÷ 500 × 100 = 86.4%.

For an overall percentage across subjects, add up all the marks scored and all the maximum marks first, then divide. Averaging the subject percentages gives a different answer when subjects have different maximum marks. Some boards and universities use their own conversions (for example CGPA × 9.5 under CBSE's former grading scheme), so check your institution's rule before quoting a converted figure.

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Questions about the percentage calculator

How do I calculate percentage increase?

Subtract the old value from the new value, divide by the old value and multiply by 100. From 80 to 100: 20 ÷ 80 × 100 = 25%.

What's the difference between percentage change and percentage difference?

Percentage change measures from a starting value, so its direction matters. Percentage difference compares two values against their average and is the same whichever comes first.

How do I work out my exam percentage?

Divide total marks obtained by total maximum marks and multiply by 100. Use X is what % of Y with your marks as X and the maximum as Y.

Percentage Calculator