Let’s look at an A5 Book
We know that A5 is 148.5 x 210mm.
So this will be the size of the front cover.
Obviously, it will also be the size of the back cover.
In this example we’ll say the spine is 10.4mm.
We saw how to get this measurement earlier.
By the way that’s 10.4
You have to be precise or you might as well not start -
just give it to a professional graphic designer.
Your cover will measure 307.4 x 210