The size of the Dutch oven for sourdough bread depends on the size of the loaf you are making. As a general rule, if you are making a 1kg loaf (flour + water + sourdough starter = 1kg in total), you will need a Dutch oven that is at least 4qt (or 4 litres) in volume. Here are some recommendations from various sources:

• The Pantry Mama: The round Dutch ovens used for baking sourdough bread are 5Q (around 4.7L) .
• True Sourdough: A 7 1/4 qt round shaped Dutch oven is ideal for boules up to 2kg in weight.
• Siamese Sourdough: The interior diameter of the 3 qt Dutch oven is about 7 inches, and the interior diameter of the 4.2 qt Dutch oven is about 9 inches.
• The Fresh Loaf: The Tartine Bread book recommends 7 qt, but a smaller oven will capture more of the steam which is what helps create a crispy crust.
• Felicia Graves: For most home cooks, a 5 to 7-quart Dutch oven is an excellent choice.

Its important to note that the Dutch oven should be tall, not shallow, as you need your bread to rise upwards, not outwards.