A thorough literatural review of researches on the experimental prediction of scour depths caused by jets was carried out to find out a measure of scour prediction. A new experimental equation for predicting scour depths due to a vortical or an inclined jet was developed from five hundreds of experimental data which were carefully reviewed and adopted from the previous researches. The developed equation shows 0.941 statistical correlation coefficient. It was found that the parameters governing the scour depth were the size of bed material, flow rate through unit width of spillway, and head drop across structure. The predicted scour depth could be expressed as the deepest scouring depth below tail water surface with correlation coefficient ${gamma}$ = 0.941.