Reliable roof measurements make projects go smoothly and stay on budget. Whether you’re a contractor training a new employee or a homeowner budgeting for a new roof, use this guide to accurately measure and calculate roof squares for any roof.
Step 1
Measure roof square footage
First, you’ll need to determine the roof’s total square footage
- Measure the length and width of each roof surface (include dormers), record on a sketch of the roof
- Note number of chimneys, skylights or other obstructions
- Multiply length by width for the square footage of each surface (if a triangle, divide by 2)
- Add up the square footage for each surface to get the total square footage of your roof
Step 2
Determine roof pitch factor
A steeper roof needs more materials. Pitch measures roof steepness, boosting measurement accuracy.
- Measure the number of inches the roof rises vertically every 12 inches of horizontal roof length (use a pitch app or ruler/level method)
- Record as a fraction with rise over run (ex. 4/12); the larger the rise, the steeper the roof
- Use an online roof pitch multiplier chart to determine the roof’s pitch factor (a pitch of 4/12 has a pitch factor of 1.054)
Step 3
Calculate Roof Squares
A roof square is a 10 x 10 area equal to 100 square feet of roof surface. To calculate:
- Multiply total roof square footage (Step 1) by the roof’s pitch factor (Step 2). Example: 2,134.0 ft² x 1.054 = 2,249.24 ft²
- Divide total square footage by 100. Example: 2,249.24 ft² / 100 = 22.4924, or 22.5 roof squares
- Use the number of roof squares needed to price materials
Roofing Materials
The purpose of calculating the precise measurements of a roof is to ensure you order the appropriate amount of roofing materials – whether it’s for a shingle, metal, and any other type of roof. Here are common roofing materials and considerations.
SHINGLES
Shingles are sold in bundles. Depending on type and brand, it may take a different number of bundles to make a roof square. When comparing shingle cost, remember to base price on squares and not on bundles.
METAL ROOFING
Metal roofing is great for homes in snowy regions. It’s typically sold by the sheet or panel. To determine the number of sheets or panels neeeded to cover the roof, divide the width of the roof by the sheet or panel width.
OTHER ROOFING MATERIALS
The basic roof square calculations detailed above will help estimate cost for other materials. Be sure to include the cost of leak barriers, deck protection, drip edge, rake edge, ridge vents, hip and ridge caps, etc.