![Onion Sizes size onion](https://i0.wp.com/cre8ov.com/wp-content/uploads/2013/11/2013-03-23-14.48.26.jpg?resize=940%2C701&ssl=1)
For your recipe ease (which from now on will be know as recipease)
1 medium onion (obviously the one in the middle) = about 1 C chopped onion
Where using a slightly bigger or smaller onion in your recipe is unlikely to ruin the recipe, it is helpful to know how much each size onion is likely to yield.