This morning, I was asked the following question by a customer: “I am putting headings on each page — how far from the top of the page should I come down?” This customer’s book will be A4 (297 x 210 mm). This is a very common query from our book printing customers.
Here’s how I answered the question.
My advice to people who ask this question (and there are many) is to find a book similar to the one you are writing, and which has a layout you find pleasing, then measure the margins and use those measurements in your own publication.
The rule of thumb is that the text block should not be centred vertically, but should be a little closer to the top that the bottom, so you might like to try something like 15mm from the top and 20mm from the bottom.
Left and right margins similarly should not be centred — otherwise you have a very big margin in the centre when the book is open. It is better to have a larger margin on the outside than the inside. Again, something like 20mm on the outside and 15mm on the inside might be appropriate. You should try these and see how they look. Bear well in mind when looking at the results that the inner margins of a perfect bound book will appear to be less than 15mm because you can’t lay the spine of a perfect bound book flat (at least not without breaking the spine!). If you use the figures I have given you, the book should appear to have horizontal margins of 20mm on the outsides and 20mm in the middle — which is ideal.
I can’t stress too much however that the best way to determine margins is just to find something you like, measure its margins, and use those measurements in your own publication.