As Wikipedia tells us, tonne-kilometre (tkm) — the unit of measurement used to measure the quantity and traffic of transportation used in transportation statistics, planning, and their related fields. It consists of two parameters: tonne amount and distance in kilometers. So 2 tons of cargo transported for 2 kilometers is a 4 tonne-kilometres.
One of the users filed a request for the calculator /2363/. When I was pondering about it, I found the conversation on one of the forums that the transport operator put the fare per kilometer (excluding cargo). For accounting purposes, you have to calculate the cost of the tonne-kilometers.
The calculator below makes a pretty simple thing. First, it calculates the total cost of transportation as the multiplication of distance by price per kilometer. Second, it calculates the number of tonne-kilometres as the multiplication of distance by mass of cargo. The total cost is divided by the number of tonne-kilometres, and you get the cost of transportation for 1 tonne-kilometre.
Write a comment if somebody thinking it should calculate the other way.