Use roof area, not the house footprint
Enter a measured or professionally supplied roof area. The floor area of a house does not account for roof slope, overhangs or a complex roof shape. This tool does not estimate those measurements for you. Use the same area unit for the quantity, material price and labour price.
Material waste applies only to material quantities. Labour uses the entered roof area; contingency applies to the combined subtotal. The result is a budget built from your inputs, not a contractor quote.
Compare the same scope of work
Check whether each quote includes removal and disposal, decking repairs, flashing, drainage, access equipment, permits and warranties. Missing items can make two apparent prices difficult to compare. Enter genuine local quotes and keep fixed charges outside this area-based model.
Changing the material price alone is useful only when the labour and scope stay comparable. If the project also includes other work, keep a separate renovation budget. Do not climb onto a roof to obtain measurements for this calculator.