The ideal size of a Dutch oven for sourdough bread depends on the size of the loaf and the proofing basket. Most sources recommend a Dutch oven that is between 4 and 6 quarts in volume, with a diameter that is about an inch or so bigger than the proofing basket when it is placed inside. This allows enough room for the dough to rise without spreading out too much. The round Dutch ovens used for baking sourdough bread are typically 5 quarts (around 4.7 liters) in size. However, some bakers prefer a smaller Dutch oven, such as a 4-quart size, to prevent the dough from spreading out and encourage rise. Ultimately, the size of the Dutch oven will depend on personal preference and the size of the loaf being baked.