Free tool
Roofing Calculator
Enter your roof footprint and pitch and get exactly how much to order — roofing squares, shingle bundles, and material cost, with a waste factor built in. Free, no signup for the estimate.
Shingles needed
0 sq
- Footprint area0 ft²
- Pitch factor1.00×
- Roof area0 ft²
- Squares (with waste)0 sq
- Shingle bundles0
- Material cost—
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Or download it now (PDF)How to estimate a roof
Roofing is priced by the square — 100 square feet of roof surface — so the whole estimate comes down to getting the roof area right, then converting to squares and bundles. The one step people miss is pitch: the roof is bigger than the footprint it sits on.
1. Measure the footprint
Length × width of the building gives the flat footprint the roof covers. For an L-shaped or complex building, break it into rectangles, figure each, and add them up. This is the area before pitch is applied.
2. Apply the pitch factor
A sloped roof has more surface than the ground it covers. Multiply the footprint by the pitch factor — the square root of 1 plus (rise ÷ 12) squared. A 4/12 roof is about 1.05×, a 6/12 is 1.12×, a 9/12 is 1.25×, and a 12/12 is 1.41×. The calculator reads your pitch and applies the factor automatically.
3. Convert to squares and bundles
Divide the roof area by 100 to get squares. Most architectural shingles run three bundles to the square, so multiply squares by three for bundle count. Order by the full square and round bundles up — you can’t buy a partial bundle.
4. Add a waste factor
Hips, valleys, dormers, and starter/ridge courses all mean trimmed, discarded shingles. Ten percent is the baseline for a plain gable; go to 12–15% for a cut-up roof. Steeper and busier roofs waste more, so round up rather than shave the order thin.
Measuring the job is step one. Turning it into a priced, professional quote is faster inside CrewRivet. See the concrete calculator, the job pricing calculator, or the fence calculator.
Roofing calculator FAQ
- What is a roofing square?
- A roofing square is 100 square feet of roof surface — the unit shingles, underlayment, and labor are all priced in. A bundle of architectural shingles covers about a third of a square, so three bundles make one square. Ordering and quoting in squares instead of square feet is the industry standard.
- How do I calculate roof area from the footprint?
- Your building footprint (length × width) is the flat area under the roof. A pitched roof is larger than that because it slopes. Multiply the footprint by a pitch factor — the square root of 1 plus (rise ÷ 12) squared. A 4/12 roof multiplies by about 1.05, a 6/12 by 1.12, a 12/12 by 1.41. This calculator applies the factor for you.
- How many bundles of shingles do I need?
- Most architectural (dimensional) shingles come three bundles to the square, so bundles ≈ squares × 3. Some heavier or premium shingles run four bundles per square. Always order by the full square and round bundles up — you cannot buy a partial bundle, and a short truck mid-tear-off is an expensive day.
- What waste factor should I use for a roof?
- Ten percent is the common baseline for a simple gable roof. Go to 12–15% for a cut-up roof with lots of hips, valleys, and dormers, where more shingles are trimmed and discarded. Steeper and more complex roofs waste more material, so lean high when in doubt — running out mid-course is worse than a few leftover bundles.
- Is this roofing calculator free?
- Yes — the live estimate is free with no email required. Enter your email only if you want the free Job Pricing Kit (pricing worksheet, markup cheat-sheet, and invoice + quote templates) sent to your inbox.