Actually, for that matter what size is A1, B2 and any other shape or size sheet of paper.
Paper sizes can be confusing because there are no obvious round numbers involved.
So whereas some people will know that an A4 sheet of paper is 210mm x 297mm and that when you move onto the A3 paper size (which is twice as big) you just double the shorter measurement giving 210mm x 2 = 420mm, but that you leave the 297mm untouched.
Well there’s a further twist to know about. Most people will have heard of the ‘A’ paper sizes, but then there are ‘B’ and ‘C’ sizes too.
B sizes are actually straightforward because they’re just a big bigger than A size paper. So for example if you want to know what B4 looks like, then you should visualise a sheet of paper which is just a bit bigger than an A4 sheet or 353mm x 450mm to be precise.
But why would anyone ever want a B4 sheet of paper. After all it sounds pretty non-standard – and it is.
The answer is that B paper sizes are mostly used by the printing industry because these ‘oversized’ sheets of paper allow for a printed page to go up to and beyond the edge of a sheet of paper, which allows for so called bleed.
Now in reality this is actually of interest once you start printing on B2 (707mm x 500mm) and B1 (1000mm x 707mm) respectively.
Now a B1 sheet of paper gives you 8 pieces of A4 on one side of the sheet or 16 pieces of A4 out if you include printing on both sides.
That’s the secret to how large litho printing companies can produce so much printing, so quickly. Lots of pages are printed in one pass through the printing press. Later on they are cut and trim and sometimes stitched (that’s just a fancy term for stapled) into booklets, catalogues and brochures.
And that in a nutshell is why the B range of paper sizes exists.
If you need to know how big different paper sizes are in millimetres then PrintHouse Corporation has this very useful Paper Size Guide showing you A, B and C paper sizes (C sizes are for envelopes by the way). Visit the Paper Size Guide here.