Commodity guide · appliances
Boxed household appliances typically rate class 92.5 - 125 (6 - 12 pcf) by density; refrigerators trend to the lighter end.
Major appliances are big steel boxes full of air. Washers and dishwashers commonly measure 8 - 12 pcf (class 92.5 - 100); refrigerators and freezers are lighter for their size at 6 - 8 pcf (class 125).
Worked example. A boxed washing machine: 30 × 30 × 42 in, 190 lb. That is 21.9 cu ft and 190 lb → 8.69 pcf → class 100. Run your own numbers →
Relevant class pages: class 92.5 · class 100 · class 125.
Keep the factory carton if you have it - it is engineered to the minimum cube. Strapping an uncartoned appliance to an oversized pallet costs a band. See the dedicated refrigerator page for that specific case.
Related: the full class chart · density calculator · how NMFC codes work.