Computational analysis of flow field inside a high pressure swirl injector is carried out. The effects of injection pressure and internal geometry on velocity field inside the nozzle and especially at the injector exit are studied in detail. From the velocity distribution at the exit plane, methods to determine the discharge coefficient and liquid sheet cone angle are given. To validate the computational model, the spray cone angles in the immediate vicinity of the nozzle exit were measured from photographs over the injection pressure differential range of 3.5 to 10.3 MPa. Static flow rates were measured using a flow meter over the same pressure range. The calculated results are found to be consistent with the experimental measurements. Extensive calculations were then conducted to examine the influence of swirl inlet port area and orifice diameter on discharge coefficient and spray cone angle. The results show that increase in swirl inlet port area and/or decrease in orifice diameter lead to an increase in discharge coefficient. Spray cone angle widens with a decrease in swirl inlet port area and an increase in orifice diameter. Discharge coefficient and spray cone angle are found to be insensitive to the injection pressure differential over the pressure range evaluated.