Remove the meat grinder's plate. This is the round section where the meat pushes out.
Clean the plate of the meat grinder thoroughly with soap and water. This prevents erroneous readings.
Measure across the plate of the meat grinder using a measuring tape. Take the measurement from side to side, crossing the middle of the plate.
Determine what the meat grinder's size is based on the measurement you have taken. A #5 grinder's plate is 2 1/8 inches wide, while a #8 meat grinder has a plate that is 2 3/8 inches wide. A meat grinder plate that has a measurement of 2 ¾ inches may be classified as a #10 or a #12 while a meat grinder plate with a measurement of 3 ¼ inches may be classified as a #20 or a #22. A meat grinder plate with a measurement of 3 7/8 inches is designated as #32.