It’s not uncommon to encounter recipes that call for large eggs, especially if you’re into baking—but what if you only have extra-large eggs in the fridge? Can you replace a large egg with a jumbo egg or even a medium egg? What, exactly, is the difference between jumbo and large eggs? After all, it’d be a real challenge to pick out one size of egg from another if you lined up individual eggs on the counter, so it can be hard to believe that egg sizes aren’t part of some elaborate marketing hoax, a label slapped on the box to allow grocery stores to sell these eggs of “different sizes” for a premium.

It turns out that there is a real difference between egg sizes, one that’s regulated by the United States Department of Agriculture, though it has nothing to do with the weight of each individual egg. Instead, the labeled egg size is based on average weight of a carton of a dozen eggs. So according to the USDA, a carton of a dozen jumbo eggs must weigh at least 30 ounces, while a carton of large eggs should weigh between 24 and 27 ounces. That means there could be an individual egg that weighs two ounces in either a box of jumbo or medium eggs; what matters is that the overall, average weight of the carton doesn’t exceed the weight guidelines as set by the government agency.

Now, if you’re simply scrambling some eggs, the size probably won’t make a significant difference in your overall enjoyment of the dish. Using two extra-large or jumbo eggs might give you a slightly bigger omelette on average, but you also just might get unlucky and use two smaller eggs from a heavier carton. Either way, it’ll be a plate of cooked eggs.

However, different egg sizes matter in baking because, as the American Egg Board explains, “most recipes for baked goods are formulas in which it’s important to maintain the proper proportion of liquid to dry ingredients and to have enough whole egg, white or yolk to perform the needed functions.” Most baking recipes are formulated with a large egg since that’s the most common type of egg in stores.

So in baking, if you’re only using one or two eggs, you can generally just swap out one type of egg for another, though the AEB also provides in-depth egg size conversions for bakers and cooks who really want to make sure they’re doing everything by the book. The difference really becomes stark by the time you’re supposed to be using four or five large eggs. For example, you should use four jumbo or extra-large eggs or six medium eggs to replace five large eggs.

It might be worthwhile to look into egg size conversions if you’re making a soufflé, but if you’re just looking to make a frittata or some other simple egg dish, this is a situation where size doesn’t really matter too much.