51 px in rem — 3.1875 rem, 38.25 pt
51 px is 3.1875 rem and 38.25 pt — 0.53125 inches, 13.494 mm, and 318.75% of the root font size.
- rem (root 16 px)
- 3.1875rem
- pt (points)
- 38.25pt
- pc (picas)
- 3.1875pc
- percent of root
- 318.75%
- inches
- 0.53125in
- millimetres
- 13.494mm
- centimetres
- 1.3494cm
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 51 px?
3.1875 rem — that is 51 divided by 16.
Q. How many points is 51 px?
38.25 pt. A point is 1/72 inch and an inch is 96 px, so you multiply by 0.75.
Q. What length is that?
0.53125 inches, or 13.494 mm — though a ruler on the screen will not agree.
Q. And as a percentage?
318.75% of the root font size.