40px to rem
40px = 2.5rem
At the browser default root font size of 16 px. Change it and this number changes — see below.
How it is calculated
One px is 0.0625rem, so:
40px × 0.0625 = 2.5remReversing it, 2.5rem × 16 returns 40px.
40px 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 | 40px equals |
|---|---|
| 14 px | 2.8571rem |
| 16 px (default) | 2.5rem |
| 18 px | 2.2222rem |
| 20 px | 2rem |
| 24 px | 1.6667rem |
Nearby values
| px | rem |
|---|---|
| 20px | 1.25rem |
| 24px | 1.5rem |
| 28px | 1.75rem |
| 32px | 2rem |
| 36px | 2.25rem |
| 40px | 2.5rem |
| 48px | 3rem |
| 56px | 3.5rem |
Frequently asked questions
What is 40px in rem?
2.5rem at the default 16 px root font size.
How is 40px converted to rem?
Multiply by 0.0625: 40 × 0.0625 = 2.5. To go back, multiply 2.5 by 16.
Is 2.5rem always the answer?
No. rem is relative to the root element, so 40px is 2.5rem only while that is 16 px. The table above gives the value at the sizes you are most likely to meet.