Percentage Difference Calculator

1. Enter the first value.
2. Enter the second value. Order does not matter.
3. Read the percentage difference between them.
4. See the absolute difference and the average used as the base.

Here is what each result means:

Percentage difference measures how far apart two values are, as a percentage of their average. You take the absolute difference between them, divide by the average of the two, and multiply by 100. Between 40 and 60 the difference is 20, the average is 50, so the percentage difference is 40 percent.

It is used when neither value is a natural starting point, so it treats both symmetrically. Comparing two measurements, two prices, or two results where neither is the reference all call for percentage difference. Because it uses the average as the base, swapping the two values gives exactly the same answer.

That symmetry is the key thing that sets it apart. Percentage change would give two different answers depending on which value you call the start, but percentage difference gives just one. It sits between the two values rather than viewing the gap from one side, which is why it is the fair choice when the two numbers are genuine peers.

It divides the size of the gap by the average of the two values.

1. Subtract one value from the other and take the absolute value.
2. Divide by the average of the two values.
3. Multiply by 100 for a percentage.

When one value is a clear starting point instead, the percentage increase calculator measures the change from it.

Find the percentage difference between 40 and 60.

Calculation: the absolute difference is |40 - 60| = 20, and the average is (40 + 60) / 2 = 50. So the percentage difference is 20 / 50 x 100 = 40 percent. Swapping 40 and 60 gives the same 40 percent.

They answer different questions, so the base is different.

Use percentage difference when the two values are peers, and percentage change when one is a clear before and the other an after.

Both compare two numbers, but the reference differs.

When one value is the accepted truth, percent error is the right tool; when neither is, use percentage difference.

The Gap Between the Values

A larger absolute difference raises the percentage difference directly.

The Size of the Values

The same gap is a smaller percentage when both values are large, since the average is bigger.

Both Being Close

Values near each other give a small percentage difference, near zero when they are almost equal.

Comparing Measurements

See how far two readings of the same thing differ.

Comparing Prices or Options

Judge the spread between two quotes where neither is the base.

Science and Data

Report the difference between two results symmetrically.

1. Dividing by One Value

Percentage difference divides by the average, not by either value alone. That is what percentage change does.

2. Confusing It with Percentage Change

Change needs a starting value; difference treats both values as peers.

3. Forgetting the Absolute Value

Percentage difference is never negative, since it uses the size of the gap.

4. Using It with a True Value

When one value is the accepted truth, use percent error instead.

5. an Average of Zero

If the two values average to zero, the percentage difference is undefined.

The arithmetic is exact; only the displayed decimals are rounded.

It measures how far apart two values are as a percentage of their average. Take the absolute difference, divide by the average of the two, and multiply by 100. Between 40 and 60 it is 40 percent.

Subtract one value from the other and take the absolute value, divide by the average of the two, then multiply by 100. This tool does it and shows the absolute difference and average.

No. Percentage difference uses the average as the base and the absolute gap, so swapping the two values gives exactly the same result. It is symmetric.

Percentage difference compares two peer values against their average and ignores order. Percentage change measures the change from a specific starting value and depends on which came first.

Use it when neither value is a natural reference, such as comparing two measurements, two prices, or two results where both are on equal footing.

Yes. It uses the absolute value of the gap, so it is never negative. It tells you how far apart the values are, not which is larger.

Percent error compares a measured value to a known true value and divides by that true value. Percentage difference compares two peers and divides by their average.

If the two values average to zero, the formula divides by zero, which is undefined. This happens when the values are equal in size but opposite in sign.

No. The calculation runs in your browser and nothing you enter is stored or sent anywhere, unless you choose Save, which keeps the result only on this device.

• Relative change and difference (Wikipedia).
• Percentage difference explained (Maths Is Fun).
• Percentage (Wikipedia).