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Enter the length and width of the house, the overhang and the roof pitch, and this roofing calculator works out the real sloped roof area, the number of roofing squares, the shingle bundles to order with waste, underlayment rolls, drip edge, ridge cap and an installed cost range. It is free, needs no sign-in, and uses the same formulas as the 40+ single-purpose calculators on this site for shingles, pitch, plywood, nails, underlayment, vents, metal roofing, flat roofs and cost.
Worked examples updated .
Every roofing estimate runs in the same order, and the calculator above follows it. Get the first three numbers right — footprint, pitch, roof area — and everything downstream (bundles, rolls, trim, cost) follows from them.
| Pitch | Angle | Multiplier | Roof area per 1,000 sq ft |
|---|---|---|---|
| 3/12 | 14° | 1.0308 | 1,031 sq ft |
| 4/12 | 18.4° | 1.0541 | 1,054 sq ft |
| 5/12 | 22.6° | 1.0833 | 1,083 sq ft |
| 6/12 | 26.6° | 1.1180 | 1,118 sq ft |
| 7/12 | 30.3° | 1.1577 | 1,158 sq ft |
| 8/12 | 33.7° | 1.2019 | 1,202 sq ft |
| 9/12 | 36.9° | 1.2500 | 1,250 sq ft |
| 10/12 | 39.8° | 1.3017 | 1,302 sq ft |
| 12/12 | 45° | 1.4142 | 1,414 sq ft |
15.03 squares of roof, 50 bundles to order, roughly $6,762-$9,767 installed.
The same house with a hip roof has the same 1,503 sq ft of surface but more cutting, so it takes 15% waste (52 bundles), drip edge on all four eaves (148 ft, no rakes) and 106 ft of hip and ridge cap instead of 42. See the hip roof calculator for the hip rafters.
Footprint measured outside the eaves, 10% waste, three bundles per square. For a hip roof add a further 5% or so; for heavier designer shingles that come four or five bundles to the square, use the shingle calculator and change the coverage.
| Footprint | 4/12 | 6/12 | 8/12 | 10/12 |
|---|---|---|---|---|
| 1,000 sq ft | 1,054 sq ft · 35 bundles | 1,118 sq ft · 37 bundles | 1,202 sq ft · 40 bundles | 1,302 sq ft · 43 bundles |
| 1,500 sq ft | 1,581 sq ft · 53 bundles | 1,677 sq ft · 56 bundles | 1,803 sq ft · 60 bundles | 1,953 sq ft · 65 bundles |
| 2,000 sq ft | 2,108 sq ft · 70 bundles | 2,236 sq ft · 74 bundles | 2,404 sq ft · 80 bundles | 2,603 sq ft · 86 bundles |
| 2,500 sq ft | 2,635 sq ft · 88 bundles | 2,795 sq ft · 93 bundles | 3,005 sq ft · 100 bundles | 3,254 sq ft · 108 bundles |
| 3,000 sq ft | 3,162 sq ft · 105 bundles | 3,354 sq ft · 111 bundles | 3,606 sq ft · 120 bundles | 3,905 sq ft · 129 bundles |
Every calculator on this site runs in your browser, with no sign-in and no email. Each one shows the formula it used, and the figures in the guides come from the same functions, so the two cannot disagree.
Measure the building footprint to the outside of the eaves, multiply by the pitch multiplier to get the true roof area, divide by 100 for squares, then add 10% to 20% waste depending on how cut-up the roof is. Multiply the result by the coverage figure for whatever material you are laying — three bundles per square for standard shingles.
Multiply the footprint (measured outside the eaves) by the pitch multiplier. A 2,000 sq ft footprint at 6/12 is 2,236 sq ft of roof; at 12/12 it is 2,828 sq ft.
One hundred square feet of finished roof surface. Roofing material is priced and ordered by the square, so a 2,236 square foot roof is 22.36 squares before waste is added.
At a 6/12 pitch with 10% waste, 74 bundles of standard three-bundle-per-square shingles. A steeper roof or a hip roof needs more.
Architectural shingles run about $4.50-$6.50 per square foot of roof installed, so the 40 x 30 ft house above (1,503 sq ft of roof) comes to about $6,762-$9,767. Tear-off, extra layers, steep pitch and local labour rates move the real number.
Yes. Every calculator on the site is free, with no sign-in and no email. The calculations run in your browser and nothing is uploaded or stored.
The material counts are exact for the measurements you enter. Cost figures are planning ranges for budgeting rather than quotes — pitch, complexity, tear-off layers and local labour rates all move the real number.
Work each section separately with its own pitch and add the areas. If you must average, use the steeper pitch so the order does not come up short.
The roof area and squares are the same for any material. For panel counts, trim and screws use the metal roof calculator, which works from the same roof area.