A dry test strip for measuring calcium is comprising a support, a reagent layer provided on the support, and a reagent holding layer provided on the reagent layer, and containing, as reagents, o-cresolphthalene complexone, a magnesium selective masking agent, and a pH buffer for adjusting the pH of the environment for reaction of the o-cresolphthalene complexone with calcium to 10.0-11.0, wherein such reagents are present in either the reagent layer or the reagent holding layer or the both layers.