Compare Fonts → Sans Serif → Roboto vs Oxygen

Roboto vs Oxygen

Both are sans serif faces on Google Fonts. Oxygen has the larger x-height, so it looks bigger at the same size. Oxygen 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.

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	Roboto	Oxygen	Difference
x-heightHeight of lowercase letters, as a share of the font size. Higher reads larger at the same point size.	52.8%	53.6%	0.7%
Cap heightHeight of capitals, as a share of the font size.	71.1%	72.2%	1.1%
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%	8.5%	0.6%
Stroke contrastHorizontal stroke divided by vertical. 1.0 is even; below 0.5 means strong thick-thin modulation.	0.82	0.81	0.01
Average character widthMean lowercase advance. Higher takes more horizontal space.	49.9%	50.4%	0.5%

Stroke weight: Roboto measures 9.1%, Oxygen measures 8.5%. Measured thickness of a vertical stroke. Higher is heavier on the page.
x-height: Roboto measures 52.8%, Oxygen measures 53.6%. Height of lowercase letters, as a share of the font size. Higher reads larger at the same point size.
Average character width: Roboto measures 49.9%, Oxygen measures 50.4%. Mean lowercase advance. Higher takes more horizontal space.