The Instant Roof Calculator is a great starting point to help you begin the estimation of your roofing project. The roof calculator above includes most of the roofing components necessary for your roof project.
Waste Factor Percentage has not been included and is determined by the complexity of the roof (# of facets and size of the facets). Add the waste factor measurements if you want to include it.
The Ice and Water Shield calculated is for the valleys to replace the valley metal. The Northern United States requires the installation of Ice and Water Shield in more areas to prevent Ice Dams from forming, so calculate more Ice and Water Shield in the cities where more is required.
Proper Attic Ventilation requires calculation depending on square footage of Attic and therefore varies and not included in this instant calculator.
If you don't know the measurements of the roof, there are great applications like: Roofr, Hover, and Eagleview. Roofr and Hover are the more economical options. If you want an Eagleview Premium Report, purchase it below.