CSS units·31px
31px =
1.9375rem
23.25pt

31 px in rem — 1.9375 rem, 23.25 pt

31 px is 1.9375 rem and 23.25 pt — 0.32292 inches, 8.202 mm, and 193.75% of the root font size.

rem (root 16 px)
1.9375rem
pt (points)
23.25pt
pc (picas)
1.9375pc
percent of root
193.75%
inches
0.32292in
millimetres
8.202mm
centimetres
0.8202cm

Why rem divides by 16

Because browsers default the root font size to 16 px, and rem is a multiple of it. When a reader enlarges text in their browser settings, only the parts written in rem grow — anything pinned in px stays put.

Nearby sizes

pxrem (root 16 px)pt (points)
28px1.75rem21pt
29px1.8125rem21.75pt
30px1.875rem22.5pt
31px1.9375rem23.25pt
32px2rem24pt
33px2.0625rem24.75pt
34px2.125rem25.5pt

On screen, pt and inches are still pixels

CSS fixes one inch at 96 px and one point at 1/72 inch. So 16 px is exactly 12 pt — but hold a ruler to the screen and that "inch" will not measure an inch.

Sizes you meet most

Body text at 16, small text at 14, spacing at 8, 24 and 32 — the values that keep coming back.

How to read this

  • rem = px ÷ 16, because browsers default the root font size to 16 px.
  • pt = px × 0.75, since CSS fixes an inch at 96 px and a point at 1/72 inch.
  • One pc is 12 pt, and one inch is both 96 px and 72 pt.
  • Use rem for text and spacing; keep px for hairlines such as borders.

Frequently asked questions

Q. How many rem is 31 px?

1.9375 rem — that is 31 divided by 16.

Q. How many points is 31 px?

23.25 pt. A point is 1/72 inch and an inch is 96 px, so you multiply by 0.75.

Q. What length is that?

0.32292 inches, or 8.202 mm — though a ruler on the screen will not agree.

Q. And as a percentage?

193.75% of the root font size.