Are you talking about open source only? I just tried your question on poe.com (free) and got the right answer: >A kilogram of feathers weighs the same as a kil

Are you talking about open source only? I just tried your question on poe.com (free) and got the right answer: >A kilogram of feathers weighs the same as a kilogram of feathers. The weight is equal because both quantities are measured in kilograms, which is a unit of mass. Regardless of the material being weighed, if the mass is the same, the weight will also be the same.