Square cake pans for baking layer and other kinds of cakes, are commonly 8 or 9 inches (20 or 23 cm) square with 2-inch (5 cm) sides or 13-by-9-by-2-inch (33-by-23-by-5-cm). Choose good-quality heavy metal pans. If using black steel or dark anodized aluminum, which absorbs heat faster, you may have to reduce oven temperature by 25°F (14°C).