40 px in rem — 2.5 rem, 30 pt
40 px is 2.5 rem and 30 pt — 0.41667 inches, 10.583 mm, and 250% of the root font size.
- rem (root 16 px)
- 2.5rem
- pt (points)
- 30pt · exact
- pc (picas)
- 2.5pc
- percent of root
- 250%
- inches
- 0.41667in
- millimetres
- 10.583mm
- centimetres
- 1.0583cm
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
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 40 px?
2.5 rem — that is 40 divided by 16.
Q. How many points is 40 px?
30 pt. A point is 1/72 inch and an inch is 96 px, so you multiply by 0.75.
Q. What length is that?
0.41667 inches, or 10.583 mm — though a ruler on the screen will not agree.
Q. And as a percentage?
250% of the root font size.