How Many Cups is One Medium/Large Onion?

Converting medium/large onions to cups

If you’ve ever encountered a recipe that called for “1 medium onion, diced,” you’ve probably wondered what that meant, exactly.

The first part of this problem is figuring out what a medium or large onion looks like. We dug around in our huge box of onions in the kitchen pantry, and picked out some sample onions. As explained by one of our chef instructors, a medium onion is around the size of a baseball, while a large onion is about the size of a slow-pitch softball.

After that, we peeled the onions, cut them into a medium, quarter-inch dice, and then measured the yield of each one. In our test, a medium onion yielded around 2 cups of diced onions, while a large onion yielded 3 cups of the same sized dice.

Of course, your mileage may vary, and there are variables to consider. Remember that the total measured quantity can be higher or lower based on the size of your diced onion pieces and the tightness of the pack in your measuring cup. As such, there’s a bit of wiggle room on these numbers.