How big is an A5 Compendium?
Compendiums are most usually sized to fit a particular configuration of paper. As you'd expect A5 compendiums are sized to fit A5 paper, which is 148mm wide and 210mm long - basically the size of a sheet of standard A4 paper which has been folded in half crosswise. Less widely used in printing than A4 paper, A5 sheets are handy for note taking and are used in some smaller forms. An A5 compendium also has a surprising amount of space -- enough to hold a phone or calculator and a pen and still have some space for cards or USB sticks.
Customised A5 compendiums
The covers of a compendium have to extend a short distance in each direction, past the paper they hold. This means that an A5 portfolio will tend to be about four centimetres longer and four centimetres wider than a piece of A5 paper. Exact dimensions vary, but an average size of 190mm wide by 250mm long. The depth will vary depending on what the portfolio is designed to hold.