How do I convert px to em?

Divide the pixel value by the parent element's font size. If the parent is 16px, then 24px ÷ 16 = 1.5em.

What is the difference between em and rem?

An em is relative to the font size of the parent element, while a rem is always relative to the root (html) font size. Ems compound through nesting; rems do not.

Why is the default parent font size 16?

Browsers use a default root font size of 16px, and unless a parent overrides it, that value cascades down. So 16 is a sensible starting divisor, but set it to your actual parent font size for accuracy.

What does it mean that ems compound?

Because each em is relative to its parent, nesting elements that are each 1.2em multiplies the effect — 1.2 × 1.2 = 1.44 of the grandparent. This compounding is the main thing to watch when using em.

When should I use em instead of rem?

Use em for sizing that should scale with its local context, such as padding inside a component that grows with that component's font size. Use rem when you want a value tied to the global root size instead.

How do I convert em back to px?

Multiply the em value by the parent font size. With a 16px parent, 1.5em × 16 = 24px.

Is anything uploaded?

No — the conversion runs entirely in your browser and nothing is sent anywhere.

PX to EM Converter — Gera Tools

Convert px to em

The em unit is relative to the font size of the parent element, which makes it useful for component-scoped sizing that scales with its context. This converter turns a pixel value into the equivalent em for a given parent font size, so you can move a design from fixed pixels to relative CSS units.

How it works

The conversion divides the pixel value by the parent element’s font size:

em = px ÷ parent font size (px)
px = em × parent font size (px)

The parent font size — not the root — is the divisor, because ems inherit and compound through nested elements. The default parent of 16px matches the browser’s usual root size.

Example

Convert 24px with a 16px parent:

24 ÷ 16 = 1.5em

If the parent font size were 20px instead, the same 24px would be 24 ÷ 20 = 1.2em.

Pixels	Parent	Result
24px	16px	1.5em
12px	16px	0.75em
24px	20px	1.2em

Enter your numbers and the result updates instantly, all in your browser.