How this roofing calculator works
Roof area: the footprint grows by your overhang on every side, then is multiplied by the pitch multiplier, √(1 + (rise ÷ 12)²). At 6/12 that is 1.118, which means a roof surface about 12% bigger than the floor plan under it. If you already know the roof area, choose that option and it is used as is.
Squares and waste: one square is 100 sq ft. Waste (10% gable, 15% hip by default) covers cut-offs, starters and mistakes. In the cost, waste is applied only to the material part of the price (assumed to be 40% of installed cost), because labor is not wasted.
Materials: shingle bundles are 3 per square. Synthetic underlayment is assumed at 10 squares (about 1,000 sq ft) per roll. Drip edge is sold in 10 ft pieces. Ridge cap shingles are assumed at about 25 linear feet per bundle.
Edge lengths: for a gable roof, drip edge is two eaves (2 × length) plus two sloped rakes (2 × half the width × pitch multiplier), and the ridge is the full length. For a hip roof, drip edge is the whole perimeter, and ridge cap is the short ridge (length − width) plus four hips, each √(2 + (rise ÷ 12)²) × half the width. If you only enter roof area, the outline is assumed to be 3:2, so these lengths are rough.
Cost: squares × installed price per square, plus squares × tear-off price × layers, plus your extras. Low, typical and high use the three prices you enter.
Where the default prices come from
Defaults are mid-points of published U.S. 2025-2026 cost guides, set per square of roof. Costs include materials, labor and normal installation. These are national averages and local prices can be well above or below them.
| Material | Low | Typical | High |
|---|---|---|---|
| 3-tab asphalt | $350 | $450 | $600 |
| Architectural asphalt | $450 | $600 | $800 |
| Standing-seam metal | $1,000 | $1,300 | $1,700 |
| Metal shingles | $800 | $1,000 | $1,400 |
| Concrete tile | $900 | $1,300 | $1,900 |
| Clay tile | $1,100 | $1,600 | $2,200 |
| Slate | $1,500 | $2,200 | $3,000 |
Tear-off defaults to $40 / $50 / $75 per square per layer for shingles, about $50 per square. Tile, slate and metal tear-off typically run higher, and the tool fills in higher numbers when you pick them.
Sources used to set these ranges (checked October 2026):
- Fixr: Roof replacement cost (about $4.75 per sq ft average, $3.75–$11 per sq ft, removal about $50 per square)
- HomeAdvisor: Roof replacement cost (asphalt $3–$7, metal $7–$13, slate $15–$30 per sq ft)
- HomeGuide: Standing-seam metal roof cost, metal shingles and tile roofs (standing seam roughly $9–$16 per sq ft, metal shingles $6–$14, concrete tile $7–$19, clay tile $11–$22)
- Remodeling Magazine, Cost vs. Value report for national roof replacement job costs
Factors that change your price
- Pitch and access. Steeper roofs need more safety gear and labor. Many roofers add 10–30% above about 8/12.
- Complexity. Valleys, dormers, chimneys, skylights and many small roof planes add labor and waste.
- Layers and condition. Extra layers cost more to remove. Rotten decking is usually billed per sheet of plywood.
- Material and brand. Impact-resistant shingles, copper accents and premium underlayment raise the price.
- Where you live. Labor rates, permit fees, disposal costs and storm demand vary a lot by region.
- Season and timing. Prices can jump after a hailstorm or in busy summer months.
Always get at least three written quotes, and ask what is included (tear-off, underlayment, flashing, ventilation, cleanup, warranty).