The most important thing in the calculation is to determine how you will carry out the installation and connection of wiring. There are two options: with camshaft. without boxes and switchgear. boxes (wire connections produced in podrozetnika).
Also, you should choose the method of laying cable on the floor, on the ceiling or on the walls (near the ceiling or above the floor). It is worth noting that it is better to choose one option and if there is no particular need to combine them. If you are not sure that you will be able everywhere to lay cable in the same way, it is better visually to calculate the whole route.
In the measurement of each segment note and add the length required to raskrucheny 15-20 cm to the food. boxes and podrozetnika and 30-40 cm in the shield (depending on the size of the shield length may be more, I think conventional, the housing shield 12 modules).
It is worth considering that, if you plan to install several outlets on the same wall, you can connect them with ribbon cable, that is, the power to lead in the near the other plug from her. This is the option to count separately, given the anticipated load on a particular socket.
And the last rule at the end of the calculations, the amount of increase in a big way, well, or add a few meters to spare. If you want some more rostochek, and their is never enough.