# Calculating scale for printing on paper

I will be making PDFs with maps on them. Two pages, one a4, one a3 format.

Both will print the same thing, just one is going to be larger. Question - what scale do I print on the PDF? The number. If the bounding box for the object is the same, the scales should be the same on both images, right? (here I dum out).

In example, The width of the bounding box is 6000m. I can get that the width of a3 image printed is going to be 0.4025m (and 0.2794m for a4).

So how can I get the scale? Is it just 1:6000?

The scale is simply the absolute distance on your paper devided by the actual corresponding distance in reality. So if you paper is 29,4cm (A4) this corresponds to 6km. So your scale is 1cm --> 204m or 1m --> 20000m or 1:20000 for a landscape-format A4-document (for panel-format this would be 21cm --> 6000m or 1:28500)

As an aside you cannot assume that on A3 the scale is simply double the amount of A4, because you have to consider the orientation of the document as well. Having said this although the actual area of your document is double the size the edges are not. Thus if you want to keep the orientation of your document (panel- or landscape-format) the scale changes not by the twice amount but by the following:

Panel-Format A3 (6000m --> 29,7cm)

``````scale(A3_panel_format) = scale(A4_panel_format) * 29,7 / 21
``````

Which is about 1:20000 (notice: same as scale A4_landscape_format)

Landscape-Format A3 (6000m --> 42cm)

``````scale(A3_landscape_format) = scale(A4_landscape_format) * 21 / 29,7
``````