# How many pixels is the A3 format?

The A3 format gives the dimension in centimeters, but if I draw an image programmatically I may know just the pixels, for example I have an image of 800x1200 and so on ...

So the question is: I must provide a JPEG file that fits into an A3 format, how many pixels will it be?

• It depends on pixel density, there's no fixed relationship between centimetres and pixels. Jan 9, 2013 at 18:13
• So let's say that I have to give that JPEG image to a person who prints it: do I have to know the pixel density of his printer? Jan 9, 2013 at 18:20
• @RamyAlZuhouri: You either know it or you don't. I suggest you use a different file format, like PDF, which handles this problem. Jan 9, 2013 at 18:45

Paper size of A3 `11.69 x 16.54` in inches and `29.7 x 42` in cm according to paper sizes.

Image dimension in pixels per page can be calculated using the following formula:

``````width in pixels = paper width in inches * dpi horizontal/scaling horizontal
height in pixels = paper height in inches * dpi vertical/scaling vertical
``````

if you set A3 as current paper size, and print at `200 x 100 dpi` at that page, the generated image dimension per page will be (approximately):

``````11.69 X 200dpi = 2338 pixels in width.
16.54 X 100dpi = 1654 pixels in height.
``````

Hope it helps.

• why did you take in account a different dpi density for horizontal and vertical?
– pax
Dec 15, 2014 at 11:10
• I have seen a large scale poster do this different scaling, like horizontal blinds rather vertically hanging (large cheap poster on bus stop)
– Vass
Aug 18, 2016 at 14:28

A3 format is 420mm x 297mm. A3 aspect ratio is 1:1.414 (As are all A formats)

What you're really asking is not the number of pixels to fit in an A3. What you need to know is the aspect ratio in equivalent pixels.

TO FIT IN A3 FORMAT
So, if you have a starting image of 1200x800, you have two options:
1) If you want to keep the short side the same, then crop it to 800 x 1131
2) If you want to keep the longer side the same, then expand the image to 1200 x 848. If you are printing this image, you can expand the image without distortion by adding empty border space of 24 pixels on the top and bottom.

TO PRINT IN A3 FORMAT
Printing quality is another thing to consider, since you asked about pixels:
Your screen likely displays at 72 pixels per inch. Your printer likely prints at 300 pixels per inch.

Pixel dimensions for printing in A3 with a device at 300 dpi results in an image that must be 4960 x 3508

This is determined by the pixel density. The pixel density, most of the times expressed in DPI or PPI (dots/pixels per inch), is a property of the image.

If you have an image of 900 x 600 pixels, the size at which it will be printed depends on the DPI of the image. For example, if it is set to be 300, then the image will be printed at 3 x 2 inches.

So to know how large your image will be printed in centimeters, you have to divide both width and height by the DPI value and then multiply both values with 2.54 to convert the inches to centimeters.

The other way around also works. An A3 sheet of paper is 29.7 x 42.0 centimeters. Divide by 2.54 to get the size in inches: 11.69 x 16.54. Then multiply with the DPI setting you want to get the size in pixels. With a DPI of 300 this gives you 3,507 x 4962 pixels.