Power drills come in 3 sizes; 1/4, 3/8, and 1/2-in. Size refers to the largest capacity of bit that will fit in the drill’s chuck. 3/8-in. drills are the most versatile. They’re powerful, yet light enough to easily hold and manage. Larger bits can drill bigger holes, so 1/2-in. drills are best for big, heavy-duty projects. Drills with higher RPM ratings (1200-rpm or more) are better for boring smaller holes into wood. Lower speed models are better at making larger holes into metal.