"The sheet is twenty centimeters."
Translation:A folha tem vinte centímetros.
That's what they do in Portuguese. I'm sure they wonder why we use "to be" as the verb here. I like to think that it's a property, and they are kind of saying it has that property which is 20 centimeters. Not sure how better to explain it. You will see this in a few places like age: "Eu tenho vinte anos."