Measure the length and width of each roof plane
Multiply length by width to get the area of each plane
Add the areas of all roof planes together
Account for roof pitch by using a pitch multiplier
Use the formula: roof area = flat area × pitch multiplier
Convert total square feet to roofing squares by dividing by 100
Include overhangs, dormers, and other roof features in the measurements
Verify measurements with a tape measure, satellite image, or roof plan
Round up to the nearest whole square for ordering materials