Best font size for reading books on iPhone and iPad
There is no single best size, because reading distance is yours to choose. Pick the smallest size you can read for twenty minutes without leaning in, then check it again in the evening. Tune line spacing and margins too.
Jump to the one-minute test
Why the printed-book answer does not carry over
Most guides on this topic are written for people setting type on a printed page. That page has one fixed size and one fixed distance. A phone has neither.
You decide how far the screen sits from your eyes, how bright the room is and how tired you are. A good size on the train is not always a good size in bed.
Find your size in a minute
Use a book you are already in the middle of. These are rules of thumb, not measurements.
- Hold the phone where you really read
- Use your usual posture and distance, not an arm-length test pose.
- Pick a plain page of prose
- Skip headings, captions and dialogue-heavy pages; they flatter small sizes.
- Move the size until reading feels easy
- Stop at the smallest size where you do not lean in or squint.
- Read for twenty minutes
- A size that is fine for one page can tire you by the end of a chapter.
- Check it again in the evening
- Dim light and tired eyes often want one size more, so keep a second setting in mind.
- Then adjust the lines
- Line height and margins can fix a page that still feels cramped at the right size.
Where each setting lives
justRead groups text size, font, spacing and margins in one Themes and Settings sheet.
Size, fast
justRead changes font size from a slider on the page edge or from the toolbar.
Line and word spacing
Line height, word spacing, letter spacing and paragraph spacing are separate controls, so you can open up a dense page without making the text bigger.
Margins
Page margins are set separately for portrait and landscape, and the top, bottom and sides each have their own value.
Fonts
Any font you import works, including OpenDyslexic, and the weight slider snaps to the weights the font really has.
One book or all
A setting can apply to a single book, and iPhone and iPad keep separate layouts.
What size does not change
EPUB books
The text reflows, so size, spacing and margins reshape every page.
PDF files
A PDF is a fixed page. Text size settings do not apply to it, so you zoom or change the page fit instead.
Not sure which format suits you? Read EPUB or PDF: which is better for reading.
Pair the size with light and breaks
justRead has a brightness slider on the page edge and 20-20-20 eye breaks.
A darker theme lowers glare at night; see the dark mode reader. The 20-20-20 rule explains the break habit.
Settings that suit the day rarely suit midnight, so save the size you like and revisit it with the season.
