18px → REM

18px to REM — 1.125rem at 16px Base

At the default browser root size of 16px, 18px equals 1.125rem. Formula: rem = px ÷ 16.

Last reviewed: June 28, 2026

CSS snippet

.example {
  font-size: 1.125rem; /* 18px at 16px root */
  padding: 1.125rem;
}

PX to REM formula

rem = px ÷ root font size

18px ÷ 16px = 1.125rem

Worked example: To convert 18px at a 16px root, divide 18 by 16. 18 ÷ 16 = 1.125. Write font-size: 1.125rem; instead of font-size: 18px; so text scales when users enlarge their browser default font size.

Common use cases at 18px (1.125rem)

Category	Tailwind / design use	CSS property example
Font size	text-lg (1.125rem)	`font-size: 1.125rem;`
Spacing	—	`padding: 1.125rem;`
Gap / margin	—	`gap: 1.125rem;`

  
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Also see  16px to rem
 
and  20px to rem
.
 
 
 18px to REM FAQ
How do you convert 18px to rem?
Divide 18 by the root font size. At the default 16px base: 18 ÷ 16 = 1.125rem. Formula: rem = px ÷ root font size.
What is 18px in rem at 16px base?
At a 16px root font size, 18px equals exactly 1.125rem. This is the browser default unless your project or the user changes html { font-size }.
Should I use 1.125rem or 18px in CSS?
Use 1.125rem for typography and spacing that should scale with the user's root font-size preference — important for accessibility. Reserve 18px for fixed values like 1px borders or bitmap image dimensions.
How do I convert 1.125rem back to pixels?
Multiply 1.125rem by 16: 1.125 × 16 = 18px. Reverse formula: px = rem × root font size.
Where is 18px commonly used in web design?
18px (1.125rem) maps to text-lg (1.125rem) in typical design systems. For Tailwind spacing, see —. Check the use-case table on this page for CSS property examples.
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