This study established an effect size measure for differential functioning for items and tests’ noncompensatory differential item functioning (NCDIF). The Mantel–Haenszel parameter served as the benchmark for developing NCDIF’s effect size measure for reporting moderate and large differential item functioning in test items. The effect size of NCDIF is influenced by the model, the discrimination parameter, and the difficulty parameter. Therefore, tables of NCDIF’s effect size were presented at given levels of a, b, and c parameters. In addition, a general effect size recommendation for moderate and large NCDIF is also established.