This research investigated the effective conditions to dye cotton with commercial indigo leaf powder. We tested dyeing conditions of: pH of dyebath (6.5, 9-12), heating ($20^{circ}C$, $50^{circ}C$, $70^{circ}C$, $90^{circ}C$), ageing (0, 0.5, 1, 4, 24 hours), reduction time (0, 30, 60 min), and dyeing temperature ($2^{circ}C$, $10^{circ}C$, $20^{circ}C$, $50^{circ}C$, $70^{circ}C$, $80^{circ}C$), dyeing was conducted for 20 minutes. The highest K/S value was obtained when cotton was dyed using pH 11 dyebath, heated at $50^{circ}C$ for 30 minutes, aged for 24 hours at room temperature ($20^{circ}C$), reduction carried out for 30 minutes, and dyed at $50^{circ}C$. It is proposed that the K/S value is primarily influenced by the dyebath pH and dyeing temperature, followed by the presence or absence of ageing time and reduction time. The color of cotton with high K/S values was B type by Munsell hue value, which was similar to the color obtained in previous studies by freshly made indigo leaf powder and indigo leaf juice. The results indicate that the dyeing conditions established in this research are suitable to maximize the dyeability of commercial indigo leaf powder and that the indigo leaf powder can be used as a substitute for fresh indigo leaf juice.