40rem to px
40rem = 640px
At the browser default root font size of 16 px. Change it and this number changes — see below.
How it is calculated
One rem is 16px, so:
40rem × 16 = 640pxReversing it, 640px × 0.0625 returns 40rem.
40rem at other root font sizes
rem is measured against the root element, so the answer above holds only while that is 16 px. A visitor who has raised their browser's default — the accessibility setting rem exists to respect — is reading your page at one of the larger rows.
| Root font size | 40rem equals |
|---|---|
| 14 px | 560px |
| 16 px (default) | 640px |
| 18 px | 720px |
| 20 px | 800px |
| 24 px | 960px |
Nearby values
| rem | px |
|---|---|
| 20rem | 320px |
| 24rem | 384px |
| 28rem | 448px |
| 32rem | 512px |
| 36rem | 576px |
| 40rem | 640px |
| 48rem | 768px |
| 56rem | 896px |
Frequently asked questions
What is 40rem in px?
640px at the default 16 px root font size.
How is 40rem converted to px?
Multiply by 16: 40 × 16 = 640. To go back, multiply 640 by 0.0625.
Is 640px always the answer?
No. rem is relative to the root element, so 40rem is 640px only while that is 16 px. The table above gives the value at the sizes you are most likely to meet.