Compare Fonts → Sans Serif → Rubik vs Ubuntu

Rubik vs Ubuntu

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

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Rubik

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.

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 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	Rubik	Ubuntu	Difference
x-heightHeight of lowercase letters, as a share of the font size. Higher reads larger at the same point size.	52.0%	52.0%	0.0%
Cap heightHeight of capitals, as a share of the font size.	70.0%	69.3%	0.7%
x-height to cap ratioProportion of lowercase to uppercase. Higher feels more modern and open.	0.74	0.75	0.01
Stroke weightMeasured thickness of a vertical stroke. Higher is heavier on the page.	9.6%	9.7%	0.1%
Stroke contrastHorizontal stroke divided by vertical. 1.0 is even; below 0.5 means strong thick-thin modulation.	0.80	0.84	0.04
Average character widthMean lowercase advance. Higher takes more horizontal space.	53.1%	51.3%	1.8%

Average character width: Rubik measures 53.1%, Ubuntu measures 51.3%. Mean lowercase advance. Higher takes more horizontal space.
Stroke contrast: Rubik measures 0.80, Ubuntu measures 0.84. Horizontal stroke divided by vertical. 1.0 is even; below 0.5 means strong thick-thin modulation.
x-height to cap ratio: Rubik measures 0.74, Ubuntu measures 0.75. Proportion of lowercase to uppercase. Higher feels more modern and open.