Math calculator

Percentage Difference Calculator

This percentage difference calculator compares two numbers and tells you how far apart they are as a percent. Enter the two values in any order, and it works out the gap against their average, which is the proper way to measure difference when neither number is the starting point. You'll get the answer with the steps, plus the change from one to the other, so you can pick the figure you actually need.

Order does not matter
Shows the steps
Live bar
Average and gap
Change shown too

Last updated July 26, 2026 Formula: |a − b| ÷ average × 100 Published by Muhammad Younus

Compare two numbers

First value Second value

Picture it 40%

Percentage difference

40 %

Difference

Average

Change first to second

50%

The steps

|40 − 60| ÷ ((40 + 60) ÷ 2) × 100 = 40%

Quick answer

To find the percentage difference between two numbers, divide the gap between them by their average and multiply by 100, using |a − b| ÷ ((a + b) ÷ 2) × 100. For 40 and 60, the gap is 20 and the average is 50, so the percentage difference is 20 ÷ 50 × 100 = 40%. Because you divide by the average and not by either number, the order you enter them in doesn't change the result.

The basics

What is percentage difference?

Percentage difference measures how far apart two numbers are, as a percent of their average. It's the fair way to compare two values when neither one is a starting point, like two lab readings or two prices from different shops. You take the gap between them, divide by their average, and multiply by 100. Because it uses the average, the order of the two numbers doesn't change the answer.

|a − b| ÷ ((a + b) ÷ 2) × 100

Step by step

How do you calculate percentage difference?

Here's how to find the percentage difference between 40 and 60:

1
Find the gapSubtract and drop the sign: |40 − 60| = 20.
2
Find the averageAdd and halve: (40 + 60) ÷ 2 = 50.
3
Divide and multiply20 ÷ 50 × 100 = 40%, so the percentage difference is 40%.

Don't mix them up

Percentage difference vs percentage change

This trips up a lot of people, so here's the clear version. Percentage difference compares two values with no "before" or "after", so it divides by their average and is always positive. Percentage change has a clear original value and divides by that, so the order matters and it turns negative for a drop. If you're tracking something over time, like a price last month and this month, you want change, and the percentage increase calculator handles that. The result above shows the change too, so you've got both.

Pick the right one

Difference vs change vs percent error

Three percent tools sound alike but answer different questions, and picking the wrong one is where most mistakes start. Use this quick guide to grab the one you actually need. Percentage difference is for two numbers of equal standing, percentage change is for tracking one value over time, and percent error is for checking a measurement against a value you already know is correct.

Metric	Formula	Use it when	Example
Percentage difference	\|a − b\| ÷ average × 100	Comparing two values where neither is a starting point	40 and 60 → 40%
Percentage change	(new − old) ÷ old × 100	Tracking one value from an old figure to a new one	40 to 60 → +50%
Percent error	\|measured − actual\| ÷ actual × 100	Comparing a measurement against a known correct value	48 vs actual 50 → 4%

So if you're comparing two lab readings or two shop prices, you want difference. If one figure is a known correct answer and you're checking how far off a reading landed, that's percent error, not difference. And if you've got a clear "before" and "after", reach for change.

Two numbers

Percentage difference between two numbers

To get the percentage difference between two numbers, you only need the two values, since the calculator figures out the gap and the average for you. For 10 and 12, the gap is 2 and the average is 11, so the difference is 2 ÷ 11 × 100 = 18.18%. It works the same whether the numbers are tiny or huge, because everything is measured against their own average.

A common trap

Difference between two percentages

When you compare two percents, like 20% and 35%, the plain gap of 15 is called 15 percentage points, not a 15% difference. Percentage points are just the subtraction of the two percents, while a true percentage difference would divide by their average. News reports often blur this line, so it's worth keeping the two ideas apart when the numbers are themselves percentages.

Worked examples

Percentage difference examples

Two numbers	Difference
40 and 60	40%
10 and 12	18.18%
100 and 150	40%
8 and 8	0%
1 and 3	100%

FAQ

Frequently asked questions

Does the order of the two numbers matter?

No. Percentage difference divides by the average of the two numbers, so you'll get the same answer whichever value you type first. That's what makes it a fair comparison rather than a before-and-after measure.

Take the absolute difference between the two numbers, divide by their average, then multiply by 100. For 40 and 60, that's |40 − 60| ÷ ((40 + 60) ÷ 2) × 100 = 20 ÷ 50 × 100 = 40%. The order of the two numbers doesn't matter, because you use the gap and the average.

It's |a − b| ÷ ((a + b) ÷ 2) × 100. The top is the size of the gap, and the bottom is the average of the two values. Since neither number is treated as the starting point, swapping them gives the same answer.

Percentage difference treats two values fairly, with no "before" or "after", which is why it uses their average as the base. Percentage change has a clear starting value and works from that old figure instead. If you're tracking growth over time, you want change; if you're comparing two readings, you want difference.

Subtract to get the gap, ignore the minus sign, divide by the average of the two numbers, and multiply by 100. For 10 and 12, the gap is 2, the average is 11, so it's 2 ÷ 11 × 100 = 18.18%. Type both numbers above and it's done for you.

Yes. Percentage difference uses the absolute gap, so it can't be negative. That's another way it differs from percentage change, which goes negative when a value drops.

That gap is 15 percentage points, not a 15% difference. "Percentage points" is the plain subtraction of two percents, while a percentage difference would divide by their average. Mixing the two up is a common mistake in reports and news.

With percentage difference, the two readings stand on equal footing, so the average becomes the base. Percent error is different: it checks a measurement against a value you already know is correct, so it works from that accepted value. Use difference when neither number is the "true" one, and reach for percent error when one of them is.

It hits 100% when the gap between the two numbers equals their average, which happens when the larger value is three times the smaller one. For 1 and 3, the gap is 2 and the average is 2, so 2 ÷ 2 × 100 = 100%. Any pair like 5 and 15 or 20 and 60 gives the same result.

Take the gap between them, divide by the average of the two, and multiply by 100. That turns the raw difference into a percentage that's fair to both numbers. If one number is really a baseline you're measuring from, use percentage change instead, which divides by that starting value.

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