Home & Energy calculator
Turn a building’s length, width, and pitch into roof area, pitch angle and grade, and roofing squares — or switch to Materials & Cost for shingle bundles, metal panel area and sheet weight, or flat-membrane area, plus an estimated installed cost.
Free, no signup — not a substitute for an on-site measurement.
Pick a mode below: roof area and squares from your building’s footprint and pitch, or materials and cost from a known number of squares.Use the button in the area result to carry your squares straight into Materials & Cost.
0 = flat roof. 6 = a 6/12 pitch (common).
~10% simple gable, 12-15% hip, 15-20%+ complex/valleys.
Roof area
1,342 sq ft
Footprint 1,200 sq ft x 1.118 pitch factor
Squares to order
14.8
Exact: 14.76, incl. 10% waste
Pitch angle
26.6°
50% grade
Pitch multiplier
1.118
Sloped area ÷ footprint area
At a glance
Pitch multiplier
Multiplier = sqrt((Rise / 12)^2 + 1)Rise is inches of rise per 12 inches of run. A flat roof (rise 0) gives a multiplier of exactly 1.
Roof area
Roof area = Footprint area x Pitch multiplierFootprint = building length x width, plus any eave overhang on each side.
Roofing squares
Squares = Roof area x (1 + Waste%) / 100One roofing square = 100 sq ft, the standard unit materials are sold and installed by.
Asphalt shingles. 3 bundles per square is the near-universal standard for both 3-tab and architectural (dimensional) shingles, though some heavier architectural products need 4 — check the wrapper. Typical 2026 US installed cost runs about $3.43-$4.65/sq ft for 3-tab and $4.11-$5.57/sq ft for architectural.
Metal panels. Steel runs about $10-$14/sq ft installed, aluminum $11-$17/sq ft, and standing-seam profiles $10-$16/sq ft in 2026 — this calculator estimates area and cost the same way as shingles, plus an independent sheet-weight calculator (Weight = Length x Width x Thickness x 7.85) for corrugated GI/GC sheet common in India, the UK, and elsewhere, using either a thickness in mm or a standard gauge (16-26 ga).
Flat roofs. A pitch (rise) of 0 gives a multiplier of 1, so roof area equals footprint area exactly — appropriate for TPO, EPDM, or modified-bitumen membrane roofs, which run roughly $7/sq ft installed in 2026.
India, the UK, and metric regions. The area, pitch, and squares math is unit-agnostic — switch to meters and the same formulas apply. A roofing square remains the standard 100 sq ft (about 9.29 m²) trade unit even where the rest of a project is quoted in metric. This tool does not cover RCC (reinforced cement concrete) slab roofing, common in Indian residential construction, since that is a structural concrete calculation rather than a roofing-material one.
Roof area & squares. A 40 ft x 30 ft building (1,200 sq ft footprint) with a 6/12 pitch: multiplier = √((6/12)² + 1) ≈ 1.118, so roof area ≈ 1,200 × 1.118 ≈ 1,342 sq ft. With a 10% waste allowance, that’s 1,476 sq ft ÷ 100 ≈ 14.8 squares to order. The pitch itself is about 26.6°, or a 50% grade.
Materials & cost. 15 squares of 3-tab shingle at 3 bundles/square needs 45 bundles; at $400/square installed, that’s an estimated $6,000.
It turns a building's footprint (length x width) and roof pitch into the actual sloped roof surface area, since a pitched roof always has more surface area than the flat footprint below it. Area = Footprint x Pitch multiplier, where the multiplier is √((rise/12)² + 1) for a roof pitched at "rise" inches per 12 inches of run. Add a waste allowance and divide by 100 to get roofing squares — the standard 100-square-foot unit roofing materials are sold in.
Multiply the roof's footprint area (length x width, plus any eave overhang) by the pitch multiplier for your roof's slope. A flat roof has a multiplier of 1 (area equals footprint); a 6/12 pitch has a multiplier of about 1.118, so a 1,200 sq ft footprint becomes roughly 1,342 sq ft of actual roof surface.
One roofing square equals 100 square feet. It is the standard unit roofing materials (shingles, underlayment, metal panels, membrane) are quoted, sold, and installed by, so a 2,400 sq ft roof is "24 squares" before any waste allowance.
Roof pitch is usually expressed as "rise per 12" — how many inches the roof rises for every 12 inches of horizontal run, e.g. a 6/12 pitch rises 6 inches per foot of run. Enter that rise number and this calculator shows the equivalent angle in degrees (arctan(rise/12)) and grade percentage (rise/12 x 100), alongside the area-multiplier it produces.
Yes — select Metal Panel in Materials & Cost for area and cost, and turn on "Calculate metal sheet weight" for an independent calculation of how much a given sheet size, gauge/thickness, and quantity weighs, using the standard steel-sheet weight formula. It does not calculate panel count from roof geometry, since that depends on your actual panel width and roof-plane dimensions, not just total area.
Weight (kg) = Length (m) x Width (m) x Thickness (mm) x 7.85 — 7.85 being steel's density in g/cm³ folded into the unit conversion. Enter your sheet size and either a thickness in mm or a common gauge (16-26 ga, converted for you), plus the quantity, and the calculator gives weight per sheet and the total in kg and lb.
No — this calculator computes area from the length, width, and pitch you enter; it does not pull imagery from a satellite, map, or address lookup. For that kind of automated aerial measurement, you'd need a dedicated aerial-measurement service or a professional report (often used by roofing contractors) — enter whatever length, width, and pitch that report gives you here to get the square and material numbers.
No — this is an independent calculator built by Calculator Matters and is not affiliated with, endorsed by, or produced by RoofingCalculator.com, Homewyse, or any other roofing-estimate website or lead-generation service. It performs its own area, pitch, materials, and cost math using the published industry formulas described on this page, not any other site's proprietary pricing or data.
Yes, for corrugated metal (GI/GC) sheet roofing — a common roofing material in India — select Metal Panel and use the sheet-weight calculator with your sheet's thickness or gauge. This tool does not cover RCC (reinforced cement concrete) flat-slab roofing, which is a structural concrete calculation, not a roofing-material one — for that, a concrete volume/quantity calculator is the right tool.
Yes — switch the units to meters in Roof Area & Squares; the pitch and squares math works the same way (a roofing square is still 100 sq ft/9.29 m² of coverage, the trade unit most materials are still quoted against even where dimensions are metric). Enter your own local material and labor costs, since these vary by country.
In the USA, installed costs run roughly $3.50-$6.50 per sq ft ($350-$650 per square) for asphalt shingles depending on tier, $7-$30 per sq ft for metal depending on type, and around $7 per sq ft for a flat TPO membrane — all before a local quote. The Materials & Cost mode pre-fills a starting cost per square for each material type; replace it with an actual bid for an accurate total.
This is a free, online calculator — no app, signup, or download required. It works the same in any modern browser on desktop or mobile.
Not as a separate download, but every formula on this page is written out in full in the Formula section below, so you can rebuild the same area, pitch, and squares math directly in a spreadsheet: =Footprint*SQRT((Rise/12)^2+1) for roof area, and that result *(1+Waste%)/100 for squares.
Yes — enter a pitch (rise) of 0 in Roof Area & Squares, which gives a pitch multiplier of exactly 1 (no slope adjustment), so the roof area equals the footprint area. Select Flat Membrane in Materials & Cost for a membrane-appropriate area and cost estimate.
Yes — choose 3-Tab Shingle or Architectural Shingle in Materials & Cost. Both default to 3 bundles per roofing square (the near-universal standard), though some architectural/dimensional shingles need 4 bundles per square — check your product's coverage and adjust the "bundles per square" figure if so.
The pitch-multiplier and roof-area formulas follow commonly published roofing-estimation methods, cross-checked against three independent sources for the same result. The sheet-weight formula uses steel's standard density (7.85 g/cm³). Material costs are general, sourced 2026 US starting points, not a live data feed.
Home & energy disclaimer
This calculator estimates roof area, roofing squares, materials, and cost from the dimensions, pitch, and figures you enter — it does not measure your actual roof from a photo, satellite image, or address, and it is not a substitute for a licensed roofer's on-site measurement and quote. Complex roof shapes (multiple planes, dormers, valleys) need to be measured and added plane by plane for an accurate total. Material costs, coverage rates, and waste needs vary by region, product, and roof complexity, and change over time — confirm current figures with a local supplier or contractor before purchasing.
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