Percentage Calculator

Calculate percentages, percentages of a number, or the original value from a percentage result.

Choose calculation type

The formula

What is X% of Y? Answer = Y × X ÷ 100
X is what percent of Y? Answer = X ÷ Y × 100
X% of what number is Y? Answer = Y × 100 ÷ X
X
In the first and third modes this is a percentage. In the second it is a part of a whole.
Y
In the first mode the whole. In the second the whole. In the third the result you already have.

Worked example

Three questions about the same shopping trip, one for each mode.

All three modes describe the same relationship — pick the one whose unknown is the thing you do not have.

Choosing the right mode

The fastest way to pick is to name the missing quantity. If you know a percentage and a total and want the amount, use the first mode. If you have two amounts and want to know how they relate, use the second. If you know the amount and the percentage it represents but not the original total — a discounted price, a commission, a partial payment — use the third. The third mode is the one people reach for least and need most, because reversing a percentage in your head is genuinely error-prone.

Percentage of versus percentage off

These are one subtraction apart and confusing them is the most common mistake here. Twenty percent of 240 is 48. Twenty percent off 240 is 240 − 48 = 192. This calculator returns the first. If you want the discounted price, subtract the result from the original, or use a dedicated discount calculator that does it in one step.

Percentage points are not percent

If a rate moves from 4 percent to 5 percent, that is a rise of one percentage point and a rise of 25 percent — 1 ÷ 4 × 100. Both statements are true and they describe the same change, which is exactly why the distinction gets abused. When you read or write a claim about a rate changing, check which unit is meant; the second mode of this calculator gives you the relative figure.

Reversing a percentage change needs care

A number that falls by 20 percent does not return to where it started when it rises by 20 percent. Starting at 100, a 20 percent fall gives 80; a 20 percent rise on 80 gives 96. The increase needed to undo a 20 percent fall is 25 percent, which the third mode will tell you if you ask what percent 100 is of 80.

Common questions

How do I calculate a percentage in my head?

Anchor on ten percent, which is the number with the decimal moved one place left. Ten percent of 240 is 24. One percent is 2.4. From those two you can assemble most things: 15 percent is 24 + 12 = 36, and 23 percent is 48 + 7.2 = 55.2. It is faster than it sounds and accurate enough to catch a wrong answer on a screen.

How do I find the original price before a discount?

Use the third mode, but with the percentage you paid rather than the percentage saved. If you paid 68 after 15 percent off, you paid 85 percent of the original, so ask what number 68 is 85 percent of: 68 × 100 ÷ 85 = 80. Entering 15 instead of 85 is the usual error and gives a wildly wrong answer.

Why does the calculator reject a total of zero?

Because the second and third modes divide by it. Nothing can be a percentage of zero, and no percentage of zero produces a non-zero result, so there is no answer to return rather than an error.

Can I use it for percentage increase and decrease?

Indirectly. The second mode gives you the ratio between two numbers, so to find a change you compare the difference to the original: if sales went 240 to 288, ask what percent 48 is of 240, which is 20 percent. A percentage-change calculator does that subtraction for you in one step.

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