There are many factors governing the precise measurements for text pages and margins, but here are the basic terms you are going to come across.
What size should my book be? There are no hard and fast rules other than it makes good sense to opt for a ‘popular’ size. I would recommended 12.9cm x 19.8cm (5.1″ x 7.8″). This is called B Format and is common and acceptable in both the US and UK. (this size has been traditionally used for ‘trade paperbacks’ in the US and ‘literary fiction’ in thr UK)
Margins Don’t try to make these too small just in order to cram more text on a page. Again most printers will make recommendations, often specifying minimum sizes. The inside margins (or gutter) will commonly be larger on a paperback than the outside margins as a tight binding can make it difficult to open it flat. (those of you who habitually ‘break’ the spine when reading a paperback book can skip this advice)
Suggested margin sizes for B Format layout These will work for most print suppliers and are what I use for my novels. I’ve given measurements in inches and mm. (alternatively, just find a book that looks right and measure the margins and page size – then copy)
Micrwosoft Word may not look quite the same as shown here given that there are different versions of Word and different operating systems, but the principle stays the same. Assuming you have written your novel on the standard A4 page size (or US equivalent) and in a default font and typeface like 12pt Times – the next step is to set the page size and margins. I will go through this using a B Format page size and nominal margins.
It looks daunting, but this really is a stage-by-stage guide and you start by getting the page size correct
1) Select Layout on the ‘ribbon’ (the menu at the top of your Word window) and the Size tab. On the drop down menu click on More Paper Sizes.
2) This will bring up a dialogue box with the ‘Paper‘ tab on top of the panel already selected. From the drop down menu choose Custom Size. Then type in the page width and height – in this case I’ve used the B Fornat sizes (you can use mm, cm or inches as you prefer – I’ve used cm).
3) Click the ‘Layout‘ tab on top of the panel. Make sure the box that says ‘Different odd and even’ is checked as this applies to the whole page layout and allows you to have a wider centre gutters on a double page spread (i.e. an open book).
The other thing you have to do here is set the Header and Footer spaces (they are usually set as defaults of 1.25cm). On a novel you rarely use a Header, so set that to 0, but you will want to put page numbers in so set the Footer to 1.5cm. When you get to refine the layout you may want to change the Footer space or even add a header; this is a simple process that can be tweaked later.
5) Now click the ‘Margins‘ tab on top of the panel. This where you set the margins and add the extra space for the gutter. Word sets the margins for left and right the same on every page, so you enter the width you need for the ‘outside margins’. Then you add the extra you need for the inside margins in the gutter space. (leave the gutter position as ‘Left’)
Example: If you want an outside margin of 1.5cm and an inside margin of 2.0cm you must set both to 1.5cm and then add an extra 0.5cm gutter so that the inside margins will become 2.0cm.
That will have set the page and margins in your Word document, but it’s still in 12pt Times with whatever default line spacing you had at the start. It will not yet look like a proper paperback book, so you now need to change the typeface, font, spacing, add folios and adjust indents, justification and chapter headings. It sounds harder than it is.
Note The margins appear larger on the outside of a pair of pages because Word is not strictly a publishing programme and is not set up to display your book with page one as a right hand page. It will work fine when it’s all done.