Boat Drain Plug Size Chart. What size are most oil drain plugs? 1/4 inch (0.6 centimeters), 3/8 inch (0.9 centimeters), 1/2 inch (1.3 centimeters) and 3/4 inch (1.9.

What size are most oil drain plugs? There are four common socket sizes: 1/4 inch (0.6 centimeters), 3/8 inch (0.9 centimeters), 1/2 inch (1.3 centimeters) and 3/4 inch (1.9.