This study examined the utility of the Gifted Composite (GC) formula derived from selected subtests on the "Stanford-Binet Intelligence Scales, Fifth Edition" (SB5) for evaluating intellectual giftedness. A sample of 52 children were administered both the SB5 and "Woodcock-Johnson Tests of Achievement, Third Edition" (WJ-III ACH). The ability of the Full-Scale IQ (FSIQ) and the GC to predict reading and math achievement were compared. Though both the FSIQ and GC significantly predicted standardized achievement test scores, the FSIQ explained more of the variance. Sequential regression analyses suggested that the SB5 factor scores preformed differently in their contribution of unique variance to the predictions. The inclusion of working memory scores in the calculation of the FSIQ appears to account for the difference in predictions between the FSIQ and GC for reading but not math skills.