Roof Cost Calculator
Enter your building footprint, roof pitch, and price per square foot to get the pitch-adjusted roof area and material cost.
What your result means
Material cost is the roof surface area times your price per square foot, and it already accounts for pitch. Roof area is the actual sloped surface, always bigger than the footprint. This is materials only, including underlayment at your price. Add 10 to 15% for waste and flashing, and figure labor on top at $2 to $5 a square foot.
How to use this calculator
- Measure the building length and width in feet.
- Find your roof pitch (most homes are 4:12 to 9:12).
- Get a price per sq ft from quotes or supplier (includes underlayment).
- Read base area, pitch-adjusted roof area, and total cost.
- Add 10-15% for waste, trim, and ridge/valley flashing.
The formula
Footprint area is length times width. The slope factor, the square root of 1 plus pitch-over-12 squared, scales that up to the real sloped surface. Multiply the roof area by your price per square foot for the material cost.
Worked example
Say you've got a 30 by 40 ft house at a 6:12 pitch, figuring $6 a square foot for asphalt. The footprint is 1,200 sq ft, the slope factor is about 1.12, so the actual roof is around 1,342 sq ft. Material lands near $8,050. Add 15% for waste and flashing and budget about $9,250.
Roofing material price ranges (per sq ft, material only)
| Material | Price per sq ft |
|---|---|
| 3-tab asphalt | $1 – $2 |
| Architectural asphalt | $3 – $5 |
| Metal | $8 – $14 |
| Tile | $10 – $18 |
| Slate | $15 – $25 |
Tips & gotchas
- Steeper roofs cost more. A 9:12 has about 25% more surface than a 4:12 of the same footprint.
- Material drives the price: asphalt is cheapest, slate the most expensive.
- Tearing off and hauling the old roof adds $1 to $2 a square foot.
- Get three quotes. Roofing prices swing hard between contractors.
- This is material only. Labor adds another $2 to $5 a square foot.
Frequently asked questions
How much does a new roof cost?
A typical asphalt shingle roof runs $5,000 to $15,000 installed. Metal lands at $10,000 to $30,000, and tile or slate starts around $20,000.
Does pitch affect roof cost?
Yes. A steeper roof has more surface area and is slower, more dangerous work, so both material and labor go up.
Should I include tear-off costs?
If you're replacing, yes. Add $1 to $2 a square foot to strip and haul the old roof.
What's the cheapest roofing material?
3-tab asphalt shingles, around $1 to $2 a square foot for the material itself.
How long does a roof last?
Asphalt runs 15 to 25 years, metal 40 to 70, and tile or slate 50 to 100-plus.
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