Primary material
45 bundles
Roofing shingles
Use the bundle count as a starting point, then confirm bundles per square, color lot, and pallet quantity with the supplier.
Roofing calculator
Roofing calculator for squares and shingle bundles.
Enter the roof footprint and pitch to estimate roof area, roofing squares, shingle bundles, and underlayment rolls — waste included. A 40 x 30 ft ranch at 6/12 needs about 45 bundles.
40 x 30 at 6/12
45 bundles
14.8 squares
1 square
100 sq ft
~3 bundles per square
Pitch factor
sqrt formula
sqrt(1 + (rise/12)²)
Quick roof answers
Common roof sizes
40 x 30 ranch (6/12)
45 bundles
about 14.8 squares with waste
50 x 30 footprint (6/12)
56 bundles
about 18.4 squares with waste
24 x 24 garage (4/12)
21 bundles
about 6.7 squares with waste
Footprint vs roof area
The footprint is the flat outline of the roof including overhangs — not the floor area inside. A two-story house can share the same roof footprint as a ranch. Steeper pitch adds area on top of that.
Shopping list
Shingles, underlayment, and accessories
Bundle and roll counts update from the calculator. Confirm bundles per square, roll coverage, and color lot before ordering.
Underlayment
4 rolls
Felt or synthetic underlayment
Roll coverage varies (15 lb felt is about 4 squares; synthetic covers more). Verify the roll square footage before ordering.
Accessories
Starter, ridge cap, nails, and flashing
Eaves, ridges, valleys, and penetrations need starter strip, ridge cap, roofing nails, drip edge, and flashing beyond the field shingles.
Install and safety
Roofing tools and safety gear
Roof work needs a roofing nailer or hammer, utility knife, chalk line, and proper fall-protection and ladder setup.
Formula shown
How the roofing estimate works
1. Roof area from footprint and pitch
roof area = footprint sq ft x sqrt(1 + (rise/12)²)
2. Squares and bundles
squares = roof area x (1 + waste) / 100; bundles = ceil(squares x 3)
3. Underlayment
rolls = ceil(squares / roll coverage in squares)
What this does not include
Tear-off of the old roof, decking repair, drip edge, flashing, ridge vent, ice-and-water shield, labor, permits, and disposal are separate. A complex roof with many facets also needs more waste than a simple gable.
Sources
- GAF shingle coverage — bundles per square and shingle coverage
- Owens Corning roofing — shingle bundle and square references
- Roofing square standard — 1 roofing square = 100 sq ft; pitch multiplier = sqrt(1 + (rise/12)^2)
Reviewed for estimating accuracy
Last updated: June 25, 2026
Estimate only.
This calculator is not a quote. Verify product yield, price, delivery minimums, and local conditions with your supplier or contractor before buying materials.
FAQ
Roofing calculator questions
Squares, shingle bundles, the pitch multiplier, waste, and what the material estimate leaves out.
How do I calculate roofing squares? + -
Multiply the footprint length by width, multiply by the pitch slope factor to get roof area, then divide by 100. A 40 x 30 ft footprint at a 6/12 pitch is about 1342 sq ft, or roughly 14.8 squares once 10% waste is added.
How many bundles of shingles do I need? + -
Standard architectural and 3-tab shingles use about 3 bundles per square. The 40 x 30 ft, 6/12 example needs roughly 45 bundles including waste. Always confirm bundles per square on the product you buy.
What is the roof pitch multiplier? + -
A roof that rises a given amount per 12 inches of run is longer than its flat footprint by sqrt(1 + (rise/12)^2). A 6/12 pitch is about 1.118x, an 8/12 about 1.202x, and a 12/12 about 1.414x. Steeper roofs need more material than the footprint suggests.
How much waste should I add for shingles? + -
A simple gable roof often uses about 10%. Roofs with many hips, valleys, dormers, and cuts can need 15% or more. The waste field is editable so you can match the roof complexity.
Is this a roof replacement quote? + -
No. It estimates material quantities (squares, bundles, underlayment) only. Tear-off, decking repair, flashing, labor, permits, and disposal are separate. Measure carefully or get a professional measurement before ordering.