How to Measure Roof Area

Footprint, Pitch & Slope Multiplier Method

This step-by-step article shows two ways to measure your roof area accurately: the footprint-and-pitch method (safest, done from the ground) and the on-roof tape-measure method (more accurate but requires a ladder). Both rely on multiplying the building footprint by the slope multiplier corresponding to the roof pitch — for example, a 4/12 pitch has a 1.054 multiplier. Includes a worked example for a 1,500 sq ft footprint at 6/12 pitch and links to the Roof Area Calculator.