Standardized concept inventories (CIs) have been widely used in science, technology, engineering, and mathematics education for assessment of student learning. In practice, there have been concerns regarding the length of the test and possible test-retest memory effect. To address these issues, a recent study developed a method to split a CI into two equivalent short CIs, which have been shown to provide equivalent mean score measures. However, the previous approach does not fully examine common requirements of test equating. This study extends the existing method with test equating analysis to form a revised algorithm for developing and validating equivalent short CIs. The method is applied to split the Conceptual Survey of Electricity and Magnetism (CSEM) into two half-length CSEMs (HCSEMs). Through a series of test-equating and validation analysis, the HCSEMs are confirmed to measure the same content clusters and the same construct of students' understanding as that of the original CSEM at a similar level of reliability regarding their question design features. Furthermore, a best performing equating function to convert scores among the two HCSEMs and the CSEM is identified through comparisons of four commonly used equating functions. The conversions are further validated using the existing data sets as well as a data set collected from an empirical study using randomized testing. The results confirm that the three CIs can provide equivalent measures in different subpopulations. Overall, the results from this study have shown that the revised algorithm can provide a more complete framework in developing and validating equivalent short CIs. In addition, this method can also be applied to develop and validate parallel CIs in general.