Lentils are similar to rice, as they will double or more when cooked. This means if you have 1 cup of dry lentils in a recipe, you'll end up with roughly 2 - 2 1/2 cups of cooked lentils. I usually make 2 cups of dried lentils in the instant pot, and end up with about 4-5 cups of finished lentils. A serving of lentils is about 1/4-1/2 of a cup per person.