Question 1

What is the difference between EM and PX?

Accepted Answer

PX (pixels) is an absolute unit — 16px is always 16px regardless of context. EM is relative to the parent element's font-size. If the parent is 16px, then 1em = 16px, 2em = 32px.

Question 2

What is the default browser font size?

Accepted Answer

Most browsers default to 16px. This means 1em = 16px by default. You can change the base size in this tool to match your project's root font-size setting.

Question 3

Should I use EM or REM?

Accepted Answer

REM is relative to the root element (html), making it more predictable. EM is relative to the parent element, so it compounds in nested elements. Use REM for layout and spacing, EM for text that should scale with its parent (like nested lists).

Question 4

How do I convert EM to PX?

Accepted Answer

Multiply the EM value by the base font size in pixels. For example, with a 16px base: 1.5em × 16px = 24px. This tool does the calculation instantly as you type.