I know with the new system of postage based on size as well as weight you have to be careful that you are paying enough in postage so I just wanted to check - when you are sending an envelope which is half the size of A4, how many sheets of A4 paper do you think you could put inside (folded) for the cost of one first class stamp? Feb 12, 2011 · How many A5 pages are in one A4 page? I’d like to know how many A5 pages (the pages in a book) are equivalent to one A4 page, and also how many pages would be in a book from 127 A4 pages. Basically, any information on how the pages size will change from A4 to the size of pages in a book. Conversion A2 / A4 : 1 A2 paper size = 4 x A4. Learn all about A2 and A4 paper sizes. ... Conversion between A2 paper & A4 paper. 1 A2 paper size = 4 x A4 paper sheet. Well if you are going up by 1 size from A4 to A3 (The lower the number the larger the sheet) you double the size of the shortest edge. So for instance an A4 sheet measures 210mm x 297mm making its shortest edge 210mm long. An A3 sheet measures 420mm x 297mm. so to move up a size 210 x 2 = 420. Don’t guess an item’s weight unless it is a postcard or letter that you are sure is under 100g. The only way to be certain is to weigh your item. The Weight Guide below gives indicative weights for many items.