We show that spin squeezing implies pairwise entanglement for arbitrary symmetric multiqubit states, and give a quantitative relation between the squeezing parameter and the concurrence for even and odd states, which refer to states with even or odd excitations. We prove that the even states generated from the one-axis twisting Hamiltonian are spin squeezed if and only if they are pairwise entangled; i.e., spin squeezing and pairwise entanglement are equivalent for these states. Numerical results show that this equivalence relation also holds for the one-axis twisting Hamiltonian with an external transverse field and for the two-axis counter-twisting Hamiltonian.