  We prove that for a given operator in the Standard Model (SM) with baryon
number B and lepton number L, that the operator's dimension is even (odd) if
(B-L)/2 is even (odd). Consequently, this establishes the veracity of
statements that were long observed or expected to be true, but not proven,
e.g., operators with B-L=0 are of even dimension, B-L must be an even number,
etc. These results remain true even if the SM is augmented by any number of
right-handed neutrinos with L=1.
