ISO A-Series vs Ratio Sizes: What's the Difference?

ISO vs ratio sizes at a glance

The systems are designed for different needs and can complement each other in a printable bundle: ISO files suit standard paper, while ratio files suit a range of image and frame proportions.

What are ISO A-series sizes?

ISO 216 defines the A-series paper sizes used in many countries. Familiar examples include A5 (148 × 210 mm), A4 (210 × 297 mm), A3 (297 × 420 mm), A2 (420 × 594 mm), and A1 (594 × 841 mm).

Every A-series size has the same √2 proportions. Cutting a sheet in half parallel to its shorter edge produces the next smaller size while preserving the same shape. For example, A3 can be halved to make two A4 sheets, and A4 can be halved to make A5.

Why are A-series sizes useful for Etsy printables?

Buyers in countries where A-series paper is common may want to print at home on A4 or take an A3 file to a local print shop. A buyer with an inch-based frame may instead need 8×10 or 11×14. Providing suitable formats can help international customers print without having to create their own crop.

What are ratio sizes?

A ratio describes an image's shape, rather than one specific physical print size. For example, 4:5 artwork can be printed at 4×5, 8×10, 16×20, or 24×30 while keeping the same proportions. Likewise, a 2:3 file can cover several sizes, including 4×6, 8×12, 12×18, 16×24, and 20×30.

Sellers can prepare a ratio file for a family of print sizes instead of making a separate composition for each one. The original still needs enough pixels for the physical size a buyer chooses.

Why isn't A4 just another ratio?

A4 has a ratio too, but it is not one of the common inch-based frame families. Its short-to-long proportions are approximately 1:1.414 (√2), unlike 4:5, 3:4, or 2:3. An A4 file is therefore not interchangeable with a 4:5 or 3:4 file.

To put a 4:5 composition on A4 paper, you can crop some of the artwork to fill the page or fit the entire image with a border. The same choice applies when adapting an A4 composition to an 8×10 frame. Stretching changes the artwork's proportions, so it is not a good way to match the formats.

Why should Etsy sellers offer both?

A customer printing at home in Italy may want A4 or A3 paper. A customer in the United States may be looking for an 8×10, 11×14, or 12×16 frame. They need different file shapes to get a clean result without working out the crop themselves.

A useful bundle can include A-series masters alongside selected ratio files. You do not need a separate file for every physical size: ratio files cover multiple dimensions, and ISO files cover the standard A-series sizes. Choose formats that suit the artwork rather than adding a crop that does not work just to increase the file count.

ISO A-series pixel sizes at 300 DPI

These approximate pixel dimensions are calculated from nominal ISO paper dimensions at 300 dots per inch. Rounding and export settings can cause a one-pixel difference.

A larger paper size needs more source pixels to maintain the same pixel density. A file that supports A4 at 300 DPI may not contain enough detail for a sharp A1 print. ReZise checks the resolution available for the selected output sizes before export.

How ReZise handles ISO and ratio formats

Upload your artwork once and select the ISO sizes and printable ratios that suit your listing. ReZise prepares the selected formats from the project, so you can review the crops and quality before exporting the files together.

Adjust each crop independently

The framing that works for a 4:5 file may not work for A4. Select each format, then drag or zoom the artwork until the composition looks right. You stay in control of what appears in each output.

Check the print quality

ReZise shows the resolution available for the selected print sizes. Review the quality readout, especially for larger formats such as A1, which require substantially more pixels than A5.

Explore the full Etsy printable size chart or our guide to the best resolution for Etsy printables.

Frequently asked questions