Compare Fonts → Sans Serif → IBM Plex Sans vs Roboto Flex

IBM Plex Sans vs Roboto Flex

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

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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.

Roboto Flex

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	IBM Plex Sans	Roboto Flex	Difference
x-heightHeight of lowercase letters, as a share of the font size. Higher reads larger at the same point size.	51.6%	51.4%	0.2%
Cap heightHeight of capitals, as a share of the font size.	69.8%	71.1%	1.3%
x-height to cap ratioProportion of lowercase to uppercase. Higher feels more modern and open.	0.74	0.72	0.02
Stroke weightMeasured thickness of a vertical stroke. Higher is heavier on the page.	8.6%	9.3%	0.7%
Stroke contrastHorizontal stroke divided by vertical. 1.0 is even; below 0.5 means strong thick-thin modulation.	0.83	0.80	0.03
Average character widthMean lowercase advance. Higher takes more horizontal space.	50.5%	49.5%	1.0%

Where they diverge most

Stroke weight: IBM Plex Sans measures 8.6%, Roboto Flex measures 9.3%. Measured thickness of a vertical stroke. Higher is heavier on the page.
Average character width: IBM Plex Sans measures 50.5%, Roboto Flex measures 49.5%. Mean lowercase advance. Higher takes more horizontal space.
Stroke contrast: IBM Plex Sans measures 0.83, Roboto Flex measures 0.80. Horizontal stroke divided by vertical. 1.0 is even; below 0.5 means strong thick-thin modulation.

At a glance

	IBM Plex Sans	Roboto Flex
Category	Sans Serif	Sans Serif
Weights	7	10
Variable axes	2	13
Language subsets	6	6
Designer	Mike Abbink	Font Bureau