The aim of this study was to determine the calcium requirements of broiler chickens in starter phase with the addition of phytase enzyme. This experiment used 1,200 broiler chickens (mixed sex) for 21 days rearing period in a closed house. The basal diets was corn and soybean meal which contained 0.097% Ca and 0.123% P-av. The treatments consisted of 6 diets treatment: P1 (basal diet with the addition of 0.42% non-phytate phosphorus (NPP), and then P2 to P6 were basal diet with the addition of 0.22% NPP and 1,000 FTU/kg phytase and the addition of calcium (Ca) at different levels: 0.82% (P2); 0.74% (P3); 0.66% (P4); 0.58% (P5) and 0.50% (P6). The growth performance, feed efficiency, and bone mineralization parameters were studied using Oneway ANOVA in a Completely Randomized Design. Duncan's new Multiple Ranges Test was used to separate means with significant differences. Results showed that 0.90% Ca supplementation without phytase and the reduction levels of Ca from 0.82% to 0.50% increased the amount of feed consumed by birds in all growth phases (P