Use this typography calculation when the font metrics, writing system, layout direction, rendering environment, and measurement units are known.

Pixels

Required number. Length in pixels.

Root font size (px)

Optional number. Root font size in pixels.

The cited overview of Typography supplies background for the terminology and domain context used by this tool.^[1]

Convert a length in pixels to ems for a root font size. Inputs are interpreted exactly in the displayed units and the calculation returns the following fields without presentation rounding.

Ems

Returned number. Equivalent length in ems.

• Font design, shaping engine, hinting, variable axes, fallback fonts, ligatures, language, display density, and browser rounding can change rendered text measurements.
• Root font size (px) must be at least 0.
• Use finite inputs in the displayed units, preserve source measurements and assumptions, and independently verify consequential decisions.

Measure the final shaped text in the target renderer and test the actual fonts, languages, viewport sizes, and accessibility settings used in production.

• Ems to Pixels Converter

  Convert a length in ems to pixels for a root font size.

• Pixels To Rem 16base

  CSS rem units from CSS pixels using a 16-pixel root font size.

• Rem To Pixels 16base

  CSS pixels from rem units using a 16-pixel root font size.