Liquid injection in cross flows has applications in gas-turbine engines. We have used the integral form of the conservation equations to find a cubic formula for the drop size in liquid sprays in cross flows. Similar to our work on axial liquid sprays, the energy balance dictates that the initial kinetic energy of the gas and injected liquid be distributed into the final surface tension energy, kinetic energy of the gas and droplets, and viscous dissipation incurred. Kinetic energy of the cross flow is added to the energy balance. Then, only the viscous dissipation term needs to be phenomenologically modelled. The mass and energy balance for the spray flows renders to an expression that relates the drop size to all the relevant parameters, including the gas-and liquid-phase velocities. The results agree well with experimental data for the drop size. The solution also provides for drop size-velocity cross-correlation, leading to drop-size distributions based on the gas-phase velocity distribution. These aspects can be used for estimating the drop size for practical applications and for computational simulations of liquid injection in cross flows.