How big is a staphylococcus?

They are smaller than other cells but bigger than viruses.

Bacteria range in size from 0.2-2 microns in width or diameter, and up to 1-10 microns in length for the nonspherical species. The largest known bacterium is Thiomargarita namibiensis, with spheroidal diameters from 100-750 microns. Spherical bacteria as small as 50-500 nm in diameter have been reported.

Robert A. Freitas Jr., Ralph C. Merkle, Kinematic Self-Replicating Machines, Landes BiOScience, Georgetown, TX, 2004 small