ESDU 74015 presents curves for static pressure recovery for the diffusers with or without a tailpipe. The effects of the area ratio, the divergence angle and the cross-section aspect ratio are taken into account. Curves for geometries for maximum pressure recovery are included for diffusers of given length and of given area ratio. Curves are also given of total pressure loss for diffusers with a tailpipe, and for diffusers without a tailpipe an equation enables total pressure loss to be calculated from the pressure recovery data. Various other factors that affect performance are discussed. The curves are based on data from a wide range of experimental tests.