Microwave ovens intended for home use range in internal capacity between 1 to 2 cubic feet, according to technology website CNET. External dimensions range from 10 to 14 inches high, 18 to 24 inches wide and 14 to 20 inches deep.
Typical internal capacity of most microwaves ranges between 1.4 and 1.8 cubic feet, according to CNET, but Remodeling Pros notes that some compact microwaves have as low as 0.4 cubic feet of capacity and some very large microwaves have more than 2 cubic feet of capacity. Both countertop and built-in microwaves are built in these size ranges, though only countertop microwaves are built in sizes less than 1 cubic foot.
Microwaves also vary widely in terms of weight, with compact microwaves as light as 32 pounds and built-in microwaves as heavy as 100 pounds available on the market. While larger external dimensions usually accompany larger internal capacities, there is not always a direct correlation between exterior size and interior capacity. Larger models also tend to have higher power outputs than smaller models, with the power output for most microwaves ranging between 600 and 1200 watts.
Finally, while larger microwaves are typically more expensive than smaller ones, built-in microwaves are usually more expensive than a countertop microwave of the same size.