Roof Material Calculator
Estimate roof squares, shingle bundles, underlayment rolls, and material cost from your home footprint, pitch, and roofing material. Material costs auto-fill per type.
Field materials only. Drip edge, ridge cap, starter strip, ice-and-water shield, nails, and pipe boots typically add 10–15% on top. For deck or porch surfaces over the home, see the Deck Material Calculator.
Estimate your roofing materials
Enter the home footprint, overhang, roof pitch, and material. Roof area, squares, bundles, underlayment, and total cost update instantly.
$2,137
For a 40 by 30 ft home with 6/12 pitch using 3-tab asphalt shingles.
How to use this calculator
Enter the length and width of your home at the eaves, plus the overhang on each side. Select your roof pitch in rise-over-12 format. Choose the roofing material and enter a waste factor. The tool multiplies the footprint by the pitch factor to get actual roof surface area, then converts that into squares, bundles, underlayment rolls, and total material cost.
Tips for success
- One square = 100 sq ft. Shingles, underlayment, and ice-and-water shield are all priced by the square (a roofing convention, not a real square shape).
- 3 bundles per square for asphalt. 3-tab and architectural shingles both need 3 bundles per square. Cedar shakes need 4–5 per square. Metal is sold by the panel or by the square.
- Always add waste. Simple gables need 10%, hips need 15% (valley and ridge cuts), and complex cut-ups with dormers need 20%+.
- Underlayment by the roll. Synthetic in 400 sq ft rolls (1 roll per 4 squares); 15 lb felt in 216 sq ft rolls. Double up if you're using full-coverage ice-and-water shield.
- Budget 10–15% for accessories. Drip edge, ridge cap shingles, starter strip, roofing nails, and pipe boots are extra on top of the field materials shown here.
Common mistakes
- Using flat footprint instead of roof surface. A 6/12 pitch adds 12% area; a 10/12 adds 30%. The pitch factor in this calc converts footprint to actual surface; don't skip it.
- Underestimating waste on hip and complex roofs. 10% works for simple gables only. Hip roofs need 15% minimum because every hip and valley is a diagonal cut. Multi-gable houses can need 20–25%.
- Forgetting tear-off and disposal. Most jurisdictions prohibit a third layer of shingles. Plan $600–$1,500 for tear-off labor and dumpster on a typical home before any new material goes down.
- Skipping ice-and-water shield in cold climates. Code typically requires it at eaves wherever freezing temperatures occur. Adds 1–2 squares of coverage at $50–$100 each: not a place to cut corners.
- Mismatching material to pitch. Asphalt shingles need ≥2/12 pitch; cedar shakes need ≥6/12; metal works down to 1/12. The panel above flags incompatible combinations.
This calculator assumes a simple gable roof. Hip roofs have the same surface area for the same footprint but need 15% waste minimum due to diagonal cuts. Multi-gable and cut-up roofs can need 20–25%. Code usually requires ice-and-water shield at eaves in cold climates, plus drip edge along all eaves and rakes.
How roof pitch changes the math
- Pitch factor. A 4/12 roof has a pitch factor of ~1.054 (surface area 5.4% larger than the flat footprint). A 6/12 is 1.118 (12% larger). A 12/12 is 1.414, almost 42% larger.
- Measure from the ground. Walk the perimeter for footprint length and width. You don't need to climb up and measure each plane; the pitch factor converts footprint to surface area.
- Read pitch with a level. Hold a 12 in level horizontally against the roof edge. The drop from level to roof surface at the 12 in mark is the rise. A 6 in drop = 6/12 pitch.
- Gable vs. hip. Same footprint + same pitch = same total area. The hip roof just splits the area into 4 triangular planes instead of 2 rectangular ones.
- Bundles by material. Asphalt (any type) takes 3 bundles per square. Cedar shakes need 4. Metal is sold by the panel.
FAQ
How many bundles of shingles do I need for a 1,500 sq ft roof?
A 1,500 sq ft roof equals 15 squares. With 3 bundles per square for standard asphalt, that is 45 bundles plus 10% waste, or 50 bundles total. For architectural shingles, the bundle count is the same but each bundle weighs more. Cedar shakes would need 60 to 75 bundles for the same roof.
How much does it cost to reshingle a typical house?
Material cost for 3-tab asphalt on a 20-square roof runs $2,500 to $3,500. Architectural shingles run $3,500 to $5,000. Add $4,000 to $8,000 for labor, tear-off, dumpster, and accessories if you hire a contractor. Total installed cost is typically $6,500 to $13,000 for standard asphalt on an average 2,000 sq ft home.
What is a roofing square?
One roofing square equals 100 sq ft of actual roof surface area, measured on the pitched plane not the flat footprint. Roofers price all materials by the square including shingles, underlayment, ice-and-water shield, and cedar shakes. A typical house has 15 to 30 squares of roof.
How do I figure out my roof pitch without climbing up?
Stand inside the attic and measure the rise of a rafter over 12 in of horizontal run using a level. From outside, hold a 2 ft level horizontally against the gable end siding at the eave and measure how much higher the roof is at the 12 in mark. You can also photograph the gable from ground level and estimate angle, though measured is more accurate.
How much waste factor should I add?
Add 10% waste for simple gable roofs with no dormers or valleys. Add 15% for hip roofs because of diagonal cuts at the hips and valleys. Add 20 to 25% for complex roofs with multiple gables, dormers, turrets, or cut-up layouts. Running a ridge vent, starter strip, and hip ridge shingles adds to waste beyond the field shingles.
How long does an asphalt shingle roof last?
3-tab asphalt shingles have a 20 to 25 year rated life but often need replacement at 15 to 20 years due to granule loss and cupping. Architectural shingles are rated 30 to 40 years and typically last 25 to 30. Climate matters: hot sun and large temperature swings cut shingle life by 30 to 50%. Cedar shakes last 30 to 40 years with maintenance. Standing seam metal lasts 40 to 70 years.