A refinery is usually designed to process crude feedstock with predetermined specifications. Four selected crude oils can be mixed with a calculated composition so that its blend characteristics is nearly the same as that of the said feedstock. This paper presents an application computer program of LOTUS 1-2-3 Version 2.0 or 2.2 on IBM PC, which is able to find four-crude combinations, the blend of which will have the predetermined values of four fraction composition. the for factions are IBP-2000 C, 200-4240 C dan Residue > 424 0C . other properties of these blends are calculated based on the composition of the respective blends.