Guide  ·  frames and files

Print-at-home frame sizes, measured

A3 paper is 29.7 x 42 cm (11.7 x 16.5 in). Its aspect ratio is 1:1.414. The frame sold as 30 x 40 cm has a ratio of 1:1.333. They are 3 mm apart on the short side and 20 mm apart on the long side.

Print a 30 x 40 cm file onto A3 and centre it, and you get a 2.1 cm band of bare paper along the length. Print an A3 file into a 30 x 40 cm frame and 2 cm of the image is behind the frame edge, which is usually where the composition ends.

This is why a file must be built for one stated size, and why the size belongs in the filename. Scaling to fit is not a fix; it either crops the picture or leaves a margin.

A4

Millimetres

210 x 297

Ratio

1:1.414

A3

Millimetres

297 x 420

Ratio

1:1.414

A2

Millimetres

420 x 594

Ratio

1:1.414

30 x 40 cm

Millimetres

300 x 400

Ratio

1:1.333

40 x 50 cm

Millimetres

400 x 500

Ratio

1:1.250

50 x 70 cm

Millimetres

500 x 700

Ratio

1:1.400

8 x 10 in

Millimetres

203 x 254

Ratio

1:1.250

11 x 14 in

Millimetres

279 x 356

Ratio

1:1.273

16 x 20 in

Millimetres

406 x 508

Ratio

1:1.250

18 x 24 in

Millimetres

457 x 610

Ratio

1:1.333

Two groups are interchangeable in shape. A4, A3 and A2 share 1:1.414, so one file scales cleanly between them. 40 x 50 cm, 8 x 10 in and 16 x 20 in all share 1:1.250. 30 x 40 cm and 18 x 24 in share 1:1.333. Nothing else in the table matches anything.

50 x 70 cm sits at 1:1.400, which is 1 percent off A-series. That difference is 5 mm over 70 cm and disappears behind a frame lip. It is the only near-miss worth accepting.

Print resolution is 300 dpi for anything a person stands close to. Below 200 dpi you can see the softening at arm’s length. Multiply the print size in inches by 300 to get the pixels the file must contain.

A4, 21 x 29.7 cm

Pixels at 300 dpi

2480 x 3508

File weight, JPEG

2 to 5 MB

A3, 29.7 x 42 cm

Pixels at 300 dpi

3508 x 4961

File weight, JPEG

4 to 9 MB

30 x 40 cm

Pixels at 300 dpi

3543 x 4724

File weight, JPEG

4 to 9 MB

40 x 50 cm

Pixels at 300 dpi

4724 x 5906

File weight, JPEG

7 to 14 MB

50 x 70 cm

Pixels at 300 dpi

5906 x 8268

File weight, JPEG

12 to 25 MB

A file under 1 MB will not print well at A3, whatever the listing claims. Check the pixel dimensions in your file browser before you load the paper.

Most home inkjets accept A4 as their largest sheet. A3 needs a wide-format model. So printing at home in practice means A4, and anything larger goes to a print shop or an online print service.

1. 01Paper: 200 to 250 gsm matte or satin photo paper. Standard 80 gsm office paper buckles with ink and looks like a document.
2. 02Finish: matte, not gloss. Gloss throws lamp glare back at whoever is looking at it, which in a treatment room is the client.
3. 03Print dialogue: set scaling to 100 percent or Actual size, never Fit to page. Fit to page silently resizes and your measurements are gone.
4. 04Colour: choose sRGB and the matte paper profile. Leave any Vivid or Enhance setting off; it pushes greens toward blue.
5. 05Borderless: only if your printer supports it and the file was built full-bleed. Otherwise print with the margin and trim with a steel rule.
6. 06Test: print one piece before all four. Ink and paper vary by machine.

A mount, sometimes called a passepartout, is the card border between the print and the frame. It makes a small print read as a considered object, and it changes the outer measurement.

21 x 29.7 cm (A4)

Mount border

45 mm

Frame needed

30 x 40 cm

30 x 40 cm

Mount border

50 mm

Frame needed

40 x 50 cm

40 x 50 cm

Mount border

50 mm

Frame needed

50 x 60 cm

8 x 10 in

Mount border

40 mm

Frame needed

11 x 14 in

When you total the width of an arrangement on the wall, use the outer frame measurement, not the print. A mounted A4 occupies 30 x 40 cm of wall, which is 43 percent more width than the paper.

1. 01Take the backing off one frame and measure the aperture, the opening the print sits behind.
2. 02Write it in millimetres, short side first: 297 x 420.
3. 03Divide the long side by the short side to get the ratio. 420 divided by 297 is 1.414.
4. 04Buy or request files at that ratio. Everything else needs cropping.
5. 05Keep the numbers in your phone. You will need them every time you buy a print.

Kiva Home files are named with the size in the filename, for example kiva-home_collection_autumn-2026_piece-1_30x40cm.jpg, so the frame it fits is never a guess.