Percentage Difference Calculator

Percentage Difference Calculator compares two numbers when neither one is the starting point. It divides the gap between them by their average rather than by one of them, which makes the answer symmetric: the difference between 80 and 100 is the same as the difference between 100 and 80, at 22.22 per cent.

That symmetry is the whole reason the measure exists. Percentage change needs a direction, so it gives two different answers depending on which value you start from. When you are comparing two measurements, two laboratories' results, or two products' prices, there is no original value and no direction, and dividing by the average is the fair way to express the gap.

Both interpretations are shown side by side so the distinction is visible rather than something you have to take on trust. If you are reporting growth over time, you want percentage change. If you are reporting how far apart two things are, you want this.

The page shows its working, not just its answer. Where there is a formula it is printed with your own numbers substituted in, so you can check the result rather than take it on trust -- which is the difference between a calculator you can use for something that matters and one you cannot.

Everything runs inside your browser. What you type is never uploaded, never logged and never stored, and the calculator keeps working if your connection drops after the page has loaded.

• Shows percentage difference, absolute difference, average of the two, as a change from the first and as a change from the second together, so you are not running it twice
• Prints the formula with your own figures substituted in
• Updates as you type, with no button to press and no page reload
• Copy the result in one click
• Free, no sign-up, and it runs entirely in your browser

The percentage difference calculator is used by writers, developers, students, marketers and anyone else who needs the job done once without installing software. Common cases include:

• Comparing two measurements of the same quantity
• Reporting how far apart two prices or quotes are
• Checking agreement between two methods or instruments
• Expressing a gap where neither value is a baseline