A3 dimensions: the size in cm, inches and pixels

What A3 is good for

A3 is the step up from a sheet of office paper, and the one most walls take comfortably. It is twice the area of A4, so detail that disappeared at the smaller size comes back, and it still hangs on its own without needing anything else around it. If you are printing one piece and are not sure what size, this is usually it.

How the A series reaches A3

Three folds down from A0. The full sheet is 841 × 1189 mm; halving the long side gives A1 at 594 × 841, again gives A2 at 420 × 594, and once more gives A3 at 297 × 420. At every step the number that was the width becomes the height, untouched, which is what keeps the shape constant.

The shape is 1:√2, and it is the single ratio for which cutting a sheet in two produces two sheets of the original shape. Among the sizes on these pages, A3 sits in the stretch where the doubling also comes out exact in millimetres: it is two A4 sheets, 124,740 mm² against 62,370, and half an A2, 249,480, with nothing left over either way. That is not true everywhere, as the hub explains. A layout built for A4 scales to A3 with nothing recropped, which is why the step from a test print to a wall print is usually this one.

Will your file carry A3?

The arithmetic is pixels divided by dpi equals inches, and running it backwards gives the file a size needs. A3 at 300 dpi is 3508 × 4961 pixels, roughly 17 megapixels, which a recent phone photograph will often reach on its own. At 150 dpi it drops to 1754 × 2480.

A3 is the size where a good photograph and a mediocre one start to look different. Detail that survived at A4 — the edge of a highlight, the line of a face — is now large enough to inspect. It is worth going back to the original file rather than a copy that has been through a messaging app, because the compression is invisible at small sizes and obvious here. The upload step measures the file for you and only offers what it can print sharply; miniature photography guide covers taking the photograph well enough that this question stops arising.

A3 framed, or A3 on its own

A3 is one of the two sizes we frame, which makes it the point where the decision stops being about dimensions. A framed A3 arrives ready to hang, in a 12 × 22 mm solid wood molding with plexiglass rather than glass. An unframed A3 costs less, leaves those choices open, and fits a correctly sized A3 frame; an 11 × 17 inch frame is not an exact fit. Neither is better; they suit different situations. If the print is a gift, framed removes a job from the recipient. If it is for your own wall, and you already have a frame or want to choose the molding yourself, unframed is the one to order. Our framed prints list what is included.

Check the US product size

Compare the available sizes and prices before ordering. Free UK delivery is included in every price.

Size references

ISO 216 defines the A and B paper-size series. Inch conversions use NIST’s exact definition of one inch as 25.4 mm. These are reference sizes; compare the print sizes actually available before ordering.