For regulations surrounding circle size, see: Ranking criteria
Circle size (CS) is a beatmap difficulty setting that affects the size of hit objects. Circle size values range from 0 to 10, but only values from 2 to 7 can be chosen in the beatmap editor. Other values can be used by manually editing the .osu file of a map.
In osu!standard, circle size changes the size of hit circles and sliders, with higher values creating smaller hit objects. Spinners are unaffected by circle size. Circle size is derived through the following formula:
r = 54.4 - 4.48 * CS
r is the radius measured in osu!pixels, and
CS is the circle size value.
In osu!taiko, circle size does not affect gameplay.
In osu!catch, circle size determines the size of the catcher and the fruit.
In osu!mania, circle size refers to the key count.
There are two mods that alter circle size when activated: