NED service to retrieve Diameters for a named object:
The NASA/IPAC Extragalactic Database (NED) provides a comprehensive fusion
of multi-wavelength data for hundreds of millions of objects located beyond
the Milky Way galaxy.
This service retrieves diameters, axis ratios, and position angles for a named object.
Diameters and related data, measured across the electromagnetic spectrum, have
been collected from large surveys, compilations and the literature. These include
optical diameters from SDSS, GALEX, RC3, ESO-B, ESO-LV, UGC, MCG, and many others.