The "A260 unit" is used as a quantity measure for nucleic acids. One A260 unit is the amount of nucleic acid contained in 1 mL and producing an OD of 1. The same conversion factors apply, and therefore, in such contexts:
:1 A260 unit dsDNA = 50 µg
:1 A260 unit ssDNA = 33 µg
:1 A260 unit ssRNA = 40 µg