We discuss finite-size corrections to the spiky strings in $AdS$ space which is dual to the long $mathcal{N}=4$ SYM operators of the form Tr($Delta_+ ^{J_1}phi_1Delta_+ ^{J_2}phi_2...Delta_+ ^{J_n}phi_n$). We express the finite-size dispersion relation in terms of Lambert $mathbf{W}$-function. We further establish the finite-size scaling relation between energy and angular momentum of the spiky string in presence of mixed fluxes in terms of $mathbf{W}$-function. We comment on the solution in pure NS-NS background as well.