Need anyone help to solve my problem..

1. for bidding new project, there is contingency we have to put for Cables..how do we calculate or estimate the factor for that contingency?

 

Is there some reason you cannot just spend a few hours looking at what cables you might need, how many of each, and how long they might be?

Does this include installation? If so, that could make a huge difference as the site conditions could dramatically effect both the materials and labor.