The PX to EM converter turns pixel values into em units based on the parent element's font size. EM is the most powerful unit for building components where padding, icons, and letter-spacing should all scale in proportion to the text.
EM is a relative unit where 1 equals the font size applied to the current element. In an element with a 16px font size, 1em is 16px and 1.5em is 24px. When you use EM on the font-size property itself, it is calculated against the parent element's font size.
Because EM is computed from the inherited parent font size, using em on nested elements multiplies the values: 1.2em inside 1.2em becomes 1.44 times the base size, which may be larger or smaller than you intended. To avoid this, use the REM unit for global sizing and reserve EM for proportional relationships inside a component.
1em equals the font size applied to the current element. Without any custom styles it inherits the browser default of 16px, so 1em = 16px. If the parent element's font size is 20px, then 1em inside a child equals 20px.
EM is relative to the parent (current element's) font size, while REM always references the html root element's font size. The common practice is rem for global sizing and em for relative sizes inside a component.
em = px value ÷ parent font size in px. With a 16px parent font, 24px equals 24 ÷ 16 = 1.5em.
It is ideal for properties that should grow and shrink with the text, such as button padding, icon sizes, and letter-spacing. Change only the font size and the related elements keep their proportions automatically.