How to make HTML pages print at a consistent size from Chrome?

I found a solution. The key is to ensure that in each document, the “logical page” that Chrome splits elements into for printing is the same size. E.g. if one document has lots of 200x200px squares and Chrome decides to group them in a rectangle 5×4 to print landscape, then you need to make sure that Chrome will print every other consistent document split into elements of size 1000x800px.

For documents that are simply a number of spans or inline-block divs in sequence, it suffices to have a div set to exactly your chosen width (1100px), and ensure that that div occupies the full page width in print preview. Then just make sure your CSS contains something like:

@media print {  
  @page {
    size: 297mm 210mm; /* landscape */
    /* you can also specify margins here: */
    margin: 25mm;
    margin-right: 45mm; /* for compatibility with both A4 and Letter */
  }
}

If this isn’t sufficient, then putting everything inside one or more divs with fixed size (width: 1100px; height: 800px; overflow: hidden;) does the job, as a way to force Chrome to split into the pages you want (and therefore keep elements the same size when printed).