Enter the total roof area (ft^2) and the waste percentage (%) into the Calculator. The calculator will evaluate the Roof Waste. 

Roof Waste Formula

RW = RA * WP/100


  • RW is the Roof Waste (ft^2)
  • RA is the total roof area (ft^2)
  • WP is the waste percentage (%)

To calculate Roof Waste, multiply the total roof area by the waste percentage over 100. Typically, there is approximately 10-15% waste on roof jobs.

How to Calculate Roof Waste?

The following steps outline how to calculate the Roof Waste.

  1. First, determine the total roof area (ft^2). 
  2. Next, determine the waste percentage (%). 
  3. Next, gather the formula from above = RW = RA * WP/100.
  4. Finally, calculate the Roof Waste.
  5. After inserting the variables and calculating the result, check your answer with the calculator above.

Example Problem : 

Use the following variables as an example problem to test your knowledge.

total roof area (ft^2) = 500

waste percentage (%) = 12.5