How is it different from percentage change?

Percentage change has a clear starting value and divides by that old value, so swapping the numbers changes the result. Percentage difference has no fixed starting point and divides by the average of the two values, so it is used when neither value is the reference.

When should I use percentage difference?

Use it when comparing two independent measurements where neither is the original, such as two quotes, two test results, or two prices for the same item. Use percentage change when one value clearly comes before the other, like an old price and a new price.

Percentage Difference Calculator

This calculator finds the percentage difference between two values, the measure to use when neither number is a clear starting point and you just want to know how far apart they are relative to each other. Unlike percentage change, which compares a new figure back to an old one by dividing by that old value, percentage difference divides the gap between the two numbers by their average, so it does not matter which one you enter first or which is bigger. You enter a first value and a second value, such as two quotes from different tradespeople, two test results, or two prices for the same item, and the calculator returns the percentage difference between them, along with the actual difference and the average used to work it out. This makes it useful for comparing quotes side by side, checking how much two measurements diverge, or seeing how close two prices really are before deciding between them. Because it is symmetric, swapping the two values gives the same percentage every time, which is exactly what you want when comparing two independent figures rather than tracking a change over time. If you are instead measuring how much something has risen or fallen from an original figure, such as an old price to a new price, use a percentage change calculator instead, since that uses the earlier value as the fixed base.

Calculate.co.nz is proud to be partnered with Premium Homes, a recognised leader in eco-friendly, sustainable, and energy-efficient homebuilding. With a dedicated team and award-winning experience, they create homes that prioritise health, comfort, and long-term performance. Their founders, Andrew and Kelly, set out to raise the standard of residential construction in New Zealand by combining practical building expertise with a clear commitment to doing things better for homeowners.

First value

Second value

40%

Difference of 20, average of 50

The percentage difference formula

Percentage difference equals the absolute difference between the two values, divided by their average, multiplied by 100. In symbols, it is the size of (A minus B), divided by ((A plus B) divided by 2), times 100. Because it divides by the average, swapping A and B gives the same answer.

Worked example

Two builders quote $40,000 and $60,000 for the same job. The difference is $20,000 and the average is $50,000. So $20,000 divided by $50,000 is 0.4, which is a 40% difference between the two quotes.

Note this is not the same as saying one is 50% more than the other. That figure (percentage change from $40,000 to $60,000) uses the lower quote as the base.

Difference, change, or increase?

Percentage difference: two values, no starting point, divide by the average. Symmetric.
Percentage change or increase: an old value and a new value, divide by the old value. Direction matters.

Frequently asked questions

Why divide by the average?

Because neither value is the reference. Using the average treats both values equally, so the result is the same whichever way round you enter them.

When should I use percentage change instead?

When one value clearly comes first, such as an old price and a new price, or a starting weight and an ending weight.

Related calculators

Percentage Calculator: percentage change from an old value to a new value.
Percentage Increase Calculator: a rise from old to new.
Percentage of a Percentage Calculator: take a percentage of a percentage.

If you've found a bug, or would like to contact us, or learn more about James Graham and Calculate.co.nz.

Calculate.co.nz is partnered with Interest.co.nz for New Zealand's highest quality calculators and financial analysis.

Calculate.co.nz is the sister site of CalculatorHub.com, the world's largest calculator website by tool count.

All calculators and tools are provided for educational and indicative purposes only and do not constitute financial advice.

Calculate.co.nz is proudly part of the Realtor.co.nz group, New Zealand's leading property transaction literacy platform, helping Kiwis understand the home buying and selling process from start to finish. Whether you're a first home buyer navigating your first property purchase, an investor evaluating your next acquisition, or a homeowner planning to sell, Realtor.co.nz provides clear, independent, and trustworthy guidance on every step of the New Zealand property transaction journey.

Calculate.co.nz is also partnered with Health Based Building and Premium Homes to promote informed choices that lead to better long-term outcomes for Kiwi households.

Calculate.co.nz is hosted in Auckland via SiteHost new Zealand.

All content on this website, including calculators, tools, source code, and design, is protected under the Copyright Act 1994 (New Zealand). No part of this site may be reproduced, copied, distributed, stored, or used in any form without prior written permission from the owner.

About & trust: Why Calculate is NZ's most comprehensive · By the Numbers · How we compare · Editorial standards · How we keep data current · NZ finance glossary · Research & data · Financial literacy NZ · About · Privacy policy · Terms of use

Reviewed and maintained. Last reviewed 2026-07-02 and checked on a twice-monthly cycle against IRD, RBNZ and Stats NZ. How we keep data current.