A zoning measurement = total floor area of all buildings ÷ total lot area. Often used alongside or instead of lot coverage to limit density.
California state law often allows ADUs to exceed the underlying zone's FAR limit by some margin. Specifics vary by city — check your local rules in the city pages.
Part of the BackyardADU California ADU Glossary — plain-English definitions of the regulatory, construction, and financing terms you'll encounter during a California ADU project.