A double oven can have a full width of 24, 27, or 30 inches. The majority of models you'll find on the market are 30 inches wide, and whether they're a wall oven or range doesn't typically affect their measurement. When shopping, it's important to look at the model's width as a whole to find out how much space you'll need in your kitchen when it's time for installation. A retailer may list the width of the oven cavities, but this measurement only accounts for the interior and strictly determines what size pans you can slip inside.