Roof Cost Calculator
Last updated: October 15, 2026
Estimate roofing area, waste allowance and project cost.
Starting figures illustrate this model. Enter your own measurements, quoted costs and applicable terms; this page does not retrieve live prices or provider rates.
Estimated roofing project cost
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- Area including waste: —
- Roofing squares (100 sq ft): —
- Base area cost: —
On this page
Quick summary: Estimate roofing area, waste allowance and project cost.
Read the complete guide
Updated reference sections in this guide are in English.
What this calculator estimates
Estimate roofing area, waste allowance and project cost.
How to use it
Enter Measured roof area (sq ft); Waste allowance (%); Installed cost per sq ft ($). Select Calculate to update the results.
How the calculation works
Budgeted roof area = measured sloped roof area × (1 + waste percentage/100). Multiply that area by the entered installed price per square foot. Divide budgeted square feet by 100 to display roofing squares. The amount without waste uses the original measured area.
Worked example: starting scenario
| Measured roof area (sq ft) | 2200 |
|---|---|
| Waste allowance (%) | 12 |
| Installed cost per sq ft ($) | 7.5 |
| Estimated roofing project cost | $18,480.00 |
|---|---|
| Area including waste | 2,464 sq ft |
| Roofing squares (100 sq ft) | 24.6 |
| Base area cost | $16,500.00 |
Important limitations
Measure the roof surface rather than the building footprint. The same installed unit price is applied to the waste allowance in this simple model. Confirm whether a contractor already includes waste, tear-off, decking, flashing, permits and disposal to avoid counting them twice.