Compare Fonts → Sans Serif → Roboto vs IBM Plex Sans

Roboto vs IBM Plex Sans

Both are sans serif faces on Google Fonts. Roboto has the larger x-height, so it looks bigger at the same size. IBM Plex Sans takes more horizontal space.

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Roboto

Handgloves & Quartz Jockeys

The quick brown fox jumps over the lazy dog. Pack my box with five dozen liquor jugs, then ship it to 1,842 Grove Street by 9:30 AM.

IBM Plex Sans

Handgloves & Quartz Jockeys

The quick brown fox jumps over the lazy dog. Pack my box with five dozen liquor jugs, then ship it to 1,842 Grove Street by 9:30 AM.

Measured differences

Measured from the font files. Heights and widths are shown as a share of the font size, so they compare directly at any point size.
Measurement	Roboto	IBM Plex Sans	Difference
x-heightHeight of lowercase letters, as a share of the font size. Higher reads larger at the same point size.	52.8%	51.6%	1.2%
Cap heightHeight of capitals, as a share of the font size.	71.1%	69.8%	1.3%
x-height to cap ratioProportion of lowercase to uppercase. Higher feels more modern and open.	0.74	0.74	0.00
Stroke weightMeasured thickness of a vertical stroke. Higher is heavier on the page.	9.1%	8.6%	0.5%
Stroke contrastHorizontal stroke divided by vertical. 1.0 is even; below 0.5 means strong thick-thin modulation.	0.82	0.83	0.01
Average character widthMean lowercase advance. Higher takes more horizontal space.	49.9%	50.5%	0.6%

Where they diverge most

x-height: Roboto measures 52.8%, IBM Plex Sans measures 51.6%. Height of lowercase letters, as a share of the font size. Higher reads larger at the same point size.
Stroke weight: Roboto measures 9.1%, IBM Plex Sans measures 8.6%. Measured thickness of a vertical stroke. Higher is heavier on the page.
Average character width: Roboto measures 49.9%, IBM Plex Sans measures 50.5%. Mean lowercase advance. Higher takes more horizontal space.

At a glance

	Roboto	IBM Plex Sans
Category	Sans Serif	Sans Serif
Weights	9	7
Variable axes	2	2
Language subsets	9	6
Designer	Christian Robertson	Mike Abbink