Assess the load cost of web fonts and the saving from subsetting.
Fonts block text rendering unless font-display is set to swap, so their load time directly delays contentful paint. Subsetting to the required character set is the single largest saving available. Each additional weight or style is a separate file and a separate request, which is why limiting to two or three is standard practice.
Web Font Performance
Font load time = subset size ÷ bandwidth + one round trip
Font load time = subset size ÷ bandwidth + one round trip Fonts block text rendering unless font-display is set to swap, so their load time directly delays contentful paint. Subsetting to the required character set is the single largest saving available.
Each additional weight or style is a separate file and a separate request, which is why limiting to two or three is standard practice.
This calculator takes 5 inputs: Number of font files, Average font file size, Saving from subsetting, Connection speed, Round-trip latency. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.