What percentage of 2 litres is 400 ml?

Well, isn't that a happy little question! To find out what percentage 400 ml is of 2 litres, we first need to convert both measurements to the same unit. Since 1 litre is equal to 1000 ml, 2 litres is 2000 ml. So, 400 ml is 20% of 2000 ml. Isn't that just a delightful little calculation?