Roofing Calculator
Estimate pitched-roof area, roofing squares, shingle bundles and underlayment rolls.
Free · No signup · Reviewed August 22, 2026Use the finished area you plan to cover, then refine the assumptions below.
Why it mattersConnect plan area and roof pitch to the sloped purchase area.
Reference image; figures update from your measurements.You’ll need
36 shingle bundlesProject shopping list
Use your result as a starting point, then confirm package coverage, product instructions and local requirements before purchasing.
How the calculation works
plan area × pitch factor × (1 + waste)
Enter each project area, choose the measurement system, then adjust waste and real package coverage. Packaged materials round up so the shopping list never suggests part of a box, sheet or panel.
How to use the roofing calculator
Measure the building roof footprint, enter the roof pitch as rise per 12 inches of run, and add a waste allowance. ProjectMeter converts plan area to true sloped area, roofing squares, complete shingle bundles and underlayment rolls.
Formula and guidance reviewed August 22, 2026. Always confirm the final order with product instructions and project requirements.What to measure
- 01
Measure the roof footprint
For a simple gable roof, measure the building length along the eave and the full horizontal width from eave to eave. Do not substitute the sloped rafter length for plan width, because pitch is applied separately.
- 02
Record pitch rise
Pitch is written as vertical rise for every 12 inches of horizontal run, such as 6:12. Use a safely measured plan, inspection report or contractor measurement rather than climbing an unsafe roof.
- 03
Split complex roof planes
Dormers, valleys, intersecting wings and unequal slopes create extra planes and cuts. Add simple footprint sections separately, then use a contractor takeoff for hips, ridges, valleys, starter and flashing.
- 04
Confirm package coverage
Check the exact shingle specification for bundles per square and the underlayment label for roll coverage. Product formats vary, so both defaults remain editable before purchasing.
40 × 24 ft footprint with a 6:12 pitch
- Simple gable roof
- 10% waste allowance
- 3 shingle bundles per square
- 400 sq ft per underlayment roll
The pitch factor is about 1.118. Sloped roof area with waste is about 1,181 sq ft, equal to 11.81 roofing squares. The shopping list rounds up to 36 shingle bundles and 3 underlayment rolls.
Try your own measurements ↑Compare the complete project cost
Your material quantity is only one part of a quote. Preparation, removal, access, finishing and local labour can change the installed total.
Planning guides for this calculator
Use the live model for feedback, then use these guides to verify the dimensions and material assumptions behind the result.
Interactive project checklists
Use the pre-order list before material arrives, then save the inspection and maintenance list for closeout and future care.
Roofing calculator FAQ
What is one roofing square?
A roofing square is 100 square feet of roof surface, not a 10-foot length. The calculator first adjusts plan area for pitch and waste, then divides the resulting sloped area by 100.
Does roof pitch increase material quantity?
Yes. A steeper roof has more sloped surface than its horizontal footprint. The calculator uses the geometric pitch factor derived from the entered rise over a 12-inch run.
Does this include hips, ridges and valleys?
The area estimate covers simple roof surfaces and primary shingle bundles. Linear accessories and complex cutting conditions are not fully modeled. Add separate sections and obtain a roof-specific takeoff before ordering.
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Plan accurately. Build safely.
This calculator is a planning estimate, not engineering or code approval. Follow manufacturer instructions and consult a qualified professional for structural, electrical, gas or permit-sensitive work.