FontKind helps designers and developers explore free fonts for a website. Its pairing checker shows how many home pages load two selected families and how that count compares with what you would expect from each font's popularity.

A pair of popular fonts can appear together on thousands of pages even if the combination is less common than that baseline predicts. JetBrains Mono and Space Grotesk give us a concrete example of how to read the two numbers together.

Calculate the baseline

Suppose a font appears on A of N pages and a second font appears on B of them. If the two appearances are independent, the expected number of pages loading both is A × B / N. Compare the actual count with that expectation.

Here is a worked example from FontKind's September 2026 analysis of desktop home pages in HTTP Archive. The snapshot has 6,276,350 pages. JetBrains Mono appears on 31,465, Space Grotesk on 34,836, and 4,025 load both. FontKind pairing data and methodology

const pages = 6_276_350 const mono = 31_465 const grotesk = 34_836 const observedTogether = 4_025 const expectedTogether = mono * grotesk / pages const ratio = observedTogether / expectedTogether console.log(Math.round(expectedTogether)) // 175 console.log(ratio.toFixed(1)) // 23.0

The pair appears around 23 times as often as the independence baseline would predict. In the same snapshot, Open Sans and Roboto appear together on 179,940 home pages. Their ratio is around 0.8. The larger raw count and the smaller ratio are compatible because both fonts are common individually.

Keep the two numbers together

If you report only the ratio, a pair that appears a handful of times can look exceptional because its expected count is tiny. Report the observed count alongside the ratio so the reader can see how many examples it represents.

The unit here is a desktop home page that loaded a font. A page can load a font through a widget, and the count alone cannot tell which font sets the heading or whether it is visible. The baseline is useful for comparing observed pairs under the same definition of a page and a font.