Compare Fonts → Sans Serif → Saira vs Rethink Sans

Saira vs Rethink Sans

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

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Saira

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	Saira	Rethink Sans	Difference
x-heightHeight of lowercase letters, as a share of the font size. Higher reads larger at the same point size.	51.0%	49.6%	1.4%
Cap heightHeight of capitals, as a share of the font size.	68.8%	70.0%	1.2%
x-height to cap ratioProportion of lowercase to uppercase. Higher feels more modern and open.	0.74	0.71	0.03
Stroke weightMeasured thickness of a vertical stroke. Higher is heavier on the page.	8.2%	8.5%	0.4%
Stroke contrastHorizontal stroke divided by vertical. 1.0 is even; below 0.5 means strong thick-thin modulation.	0.85	0.86	0.01
Average character widthMean lowercase advance. Higher takes more horizontal space.	52.6%	52.1%	0.6%

x-height: Saira measures 51.0%, Rethink Sans measures 49.6%. Height of lowercase letters, as a share of the font size. Higher reads larger at the same point size.
x-height to cap ratio: Saira measures 0.74, Rethink Sans measures 0.71. Proportion of lowercase to uppercase. Higher feels more modern and open.
Stroke weight: Saira measures 8.2%, Rethink Sans measures 8.5%. Measured thickness of a vertical stroke. Higher is heavier on the page.