To estimate a full roof replacement, multiply your roof’s footprint area by a pitch multiplier to get the true sloped surface area, then multiply that by your combined price per square foot for materials, labor and tear-off, and add a decking-repair allowance.
Roof Replacement Cost Calculator
Full tear-off and replacement cost for a roof, from footprint area, pitch, materials and labour.
Estimating the Cost of a Full Roof Tear-Off and Replacement
This roof replacement cost calculator prices a complete tear-off and reinstall from your roof’s footprint dimensions, its pitch (slope), and your own local per-square-foot rates for roofing material, installation labor, and tear-off and disposal. It also adds a fixed allowance for any decking repair the crew finds once the old roof is removed, since that’s rarely known until the tear-off is underway.
Roof replacement pricing depends heavily on material choice, roof complexity, region and local labor rates, so this calculator is built around your own quoted rates rather than a fixed national average. It works for any roofing material priced by the square foot — asphalt shingles, metal panels, or other systems.
This covers related searches such as roof replacement cost per square foot, new roof cost calculator, and roof tear-off and installation pricing.
Depending on what you are measuring, one of these may suit the job better: Irregular Roof Area Calculator.
How the Roof Replacement Cost Calculator Works
Total = Roof area × (Material price + Labor price + Tear-off price) + Decking allowance
Where:
- Roof area = Footprint length × Footprint width × Pitch multiplier
- Material price = roofing material cost per square foot
- Labor price = installation labor cost per square foot
- Tear-off price = removal and disposal cost per square foot of the old roof
- Decking allowance = a fixed budget for repairing or replacing damaged roof decking
Why a Pitch Multiplier?
A sloped roof has more actual surface area than its flat footprint, so the calculator multiplies the footprint by a pitch multiplier to find the true roof area to be covered.
| Roof Pitch | Pitch Multiplier |
|---|---|
| 4:12 | ≈ 1.054× |
| 6:12 | ≈ 1.118× |
| 8:12 | ≈ 1.202× |
| 12:12 | ≈ 1.414× |
Worked Example
A 40 ft × 30 ft footprint (1,200 ft²) with a 6:12 pitch (1.118 multiplier) gives a roof area of 1,200 × 1.118 = 1,341.6 ft². At $4.50/ft² material, $3/ft² labor, $1.50/ft² tear-off, plus a $400 decking allowance: Total = 1,341.6 × (4.5 + 3 + 1.5) + 400 = 1,341.6 × 9 + 400 = $12,474.40.
Related: Roof Surface Area Calculator.
Frequently Asked Questions
How much does it cost to replace a roof?
It depends on roof size, pitch, material choice and local labor rates, all of which vary widely by region — enter your own quoted rates above for an estimate specific to your roof.
What is a roofing square?
A roofing square is 100 square feet of roof surface — a standard unit contractors and material suppliers use for pricing and ordering shingles, underlayment and other materials.
Why is the roof area larger than the footprint?
Because the roof surface is sloped, not flat, its actual area is larger than the building’s footprint — the steeper the pitch, the bigger the difference, which is why the pitch multiplier is applied.
Does this include decking repair costs?
It includes a fixed allowance you set for decking repair, since the actual extent of any rotted or damaged decking usually isn’t known until the old roofing is removed.
Can I use this for a metal or shingle roof?
Yes — enter your own material price per square foot for whichever roofing system you’re installing, since the formula itself doesn’t assume a specific material.
