Front-end work constantly moves between CSS length units, and the conversions trip people up because most of them depend on a base font size rather than being fixed. A design hands you pixels, a stylesheet uses rem for accessibility, a component asks for em, a print rule wants points, and a media query thinks in percent. This converter takes a value in any of these units and instantly shows the equivalent in all of the others, so you can keep your spacing and type scale consistent without doing the arithmetic in your head. Enter a value, set the base font size, choose the unit you are converting from, choose the unit you want, and the result updates straight away alongside a full reference list. The method is simple. Each unit is expressed as how many pixels it represents. A pixel is one pixel, an em and a rem each equal the base font size, a point is 1.3333 pixels because CSS assumes 96 pixels per inch and a point is one seventy-second of an inch, and one percent is a hundredth of the base. The calculator multiplies your value by the pixels-per-unit factor for the from unit to get pixels, then divides by the factor for the to unit. With the common default base of 16 pixels, 16px is 1rem, 12pt is 16px, and 100 percent is the base size. Changing the base font size recomputes everything, which is handy when your root font size is not 16. It suits web developers, designers and anyone tuning a responsive type scale who wants a fast, transparent CSS unit conversion.
Each unit is defined by how many pixels it represents, using the base font size you enter (call it B). To convert, the calculator multiplies your value by the pixels-per-unit factor for the unit you are converting from to get pixels, then divides by the factor for the unit you want.
value in px = value × pxPer[from]
result = value in px / pxPer[to]
pxPer: px = 1, em = B, rem = B, pt = 1.3333, % = B / 100
| Unit | Pixels per unit (base B) |
|---|---|
| px | 1 |
| em | B (the base font size) |
| rem | B (the base font size) |
| pt | 1.3333 (96 / 72) |
| % | B / 100 |
This converter is for web developers and designers who need to move a length between px, em, rem, pt and percent while keeping a consistent type and spacing scale across a stylesheet.
Divide the pixel value by the base font size. At a base of 16, 16px is 1rem and 24px is 1.5rem.
A rem is relative to the root font size and an em to the current element. Here both use the base you enter, so they match.
1.3333 pixels, because a point is a seventy-second of an inch and CSS assumes 96 pixels per inch. So 12pt is 16px.
It is treated as a share of the base font size, so 100% equals the base and 50% is half the base.
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