To clarify the efficiency of internal reduction at a continuous casting strand, a series of liquid core reduction tests with various shaped ingots was carried out, and the amount of internal reduction was determined by adding tracer into the liquid core. The result was discussed by deformation analysis, using the three-dimensional Finite Element Method. Factors influencing the internal reduction efficiency were assessed, and consequently, a regression equation to estimate the amount of internal reduction for any casting shapes and conditions was derived.