16 pieces
Roofing Calculator
Enter your roof measurements once and get rafter count, roof pitch, shingle bundles, and sheathing sheets together — no re-entering the same numbers on three different pages.
Material ListRafters or trusses (this plane) Roof plane area Ridge board length Eave fascia (this plane) Soffit area Bundles to buy Adjusted roofing area Underlayment Buy sheets Base need
Roofing jobs touch at least three separate takeoffs: framing/rafter count, roof covering, and sheathing. This page runs all three from one set of roof measurements. Each calculator below is the same one available on its own page — nothing here is a new formula, it is the Roof, Shingles, and Sheathing calculators reading from a shared input set.
How to measure your roof
Measure roof length along the eave (the horizontal edge, not the sloped side) and record it as one plane at a time — a simple gable roof has two planes of the same length. For rise and run, measure from the ridge to the wall plate: run is the flat horizontal distance, rise is the vertical height gained over that run. If you already know the pitch (for example, “6 in 12”), you can enter pitch and run instead and skip measuring rise directly.
On-center spacing is the distance between the centerlines of adjacent rafters or trusses, almost always 16 or 24 inches on residential work — check your framing plan or existing rafters before assuming. Overhang run is the horizontal distance the roof extends past the wall, measured the same way as the main run.
Roof measurements
Enter these once. Rafter count and roof area come from the Roof calculator; that roof area then feeds Shingles and Sheathing automatically below.
Roof
Solves rise, run, pitch, rafter length, rafter count, roof plane area, ridge board length, eave fascia, and soffit area.
Plan for a 12.65 ft rafter at a 4:12 pitch.
Plan for
Roof result
409.12 sq ft
30 ft
30 ft
30 sq ft
Warnings
- INFO This is a general reference only. Verify local code, loading, and manufacturer requirements.
Detail values
- Rise
- 4 ft
- Run
- 12 ft
- Rafter length
- 12.65 ft
- Ridge-cut rafter length
- 12.58 ft
- Total rafter length (order length)
- 13.64 ft
- Pitch
- 4 : 12
- Angle
- 18.43 deg
- Recommended rafter size
- Data not available for this combination
- Span lookup status
- No verified row found
Assumptions
- Pitch warning reference: 2:12 minimum reference
- Overhang included in roof area: Yes
- Ridge board thickness: 1.5 in (editable; 1.5 in default matches a standard 2x ridge board)
- Rafter span table load basis: IRC "Rafter Spans for Common Lumber Species" table: 20 PSF roof live load, 10 or 20 PSF dead load, L/delta=180, ceiling not attached to rafters. Not a ground-snow-load table.
Formula details
- Rafter length: sqrt(rise^2 + run^2)
- Pitch: (rise / run) x 12
- Angle: atan(rise / run) x (180 / pi)
- Rafter count: ceil(roofLength / spacing) + 1
Per single roof plane. Multiply by the number of planes (2 for a gable, more for a hip) for the whole roof.
- Ridge-cut rafter length: rafterLength - (ridgeBoardThickness / 2) x (rafterLength / run)
Shortens the theoretical rafter length by the ridge board's half-thickness, projected onto the slope, so the ordered board matches the actual birdsmouth/ridge cut.
- Roof plane area: roofLength x totalRafterLength
Single roof plane area including overhang and the ridge-cut adjustment.
- Soffit area: roofLength x overhangRun
Underside of the overhang only; zero when no overhang is entered.
- Rafter span lookup: Use verified IRC "Rafter Spans for Common Lumber Species" table row for species, rafter size, and spacing.
Roof live load 20 PSF, L/delta=180, ceiling not attached to rafters. Not a snow-load table.
Shingles
Converts roof area into bundles or metal panels to buy, plus starter strip, drip edge, ridge cap, and underlayment.
You'll need 14 bundles of shingles for 409.12 sq ft of roof.
You'll need
Shingles result
14 bundles
4.5 squares
2 rolls
Warnings
- INFO Enter eave, rake, and ridge lengths to size starter strip, drip edge, and ridge cap. These are skipped without them.
Detail values
- Roof area used
- 409.12 sq ft
- Squares
- 4.09
- Adjusted squares
- 4.5
Assumptions
- Shingle type: Architectural / dimensional
- Coverage input: Bundles per square
- Underlayment coverage: 400 sq ft per roll (editable)
Formula details
- Squares: roofArea / 100
- Adjusted squares: squares x (1 + wastePercent)
- Bundles to buy: ceil(adjustedSquares x bundlesPerSquare)
- Drip edge: eaveLength + rakeLength
- Underlayment rolls: ceil(adjustedArea / coveragePerRoll)
Sheathing
Converts roof area into sheathing sheets to buy, with OSB/plywood and roof/wall context for the thickness spec.
You'll need 15 sheathing panels for 409.12 sq ft.
You'll need
Sheathing result
15 sheets
12.78 sheets
Detail values
- Area used
- 409.12 sq ft
- Sheet area
- 32 sq ft
- Base sheets
- 12.78
Assumptions
- Default panel size: 4 ft x 8 ft when unchanged
- Sheathing spec: 0.4375" OSB for roof sheathing (editable; not a code minimum — verify local requirements)
Formula details
- Sheet area: sheetWidth x sheetLength
- Base sheets: area / sheetArea
- Purchase sheets: ceil(baseSheets x (1 + wastePercent))
Choosing shingles vs. metal roofing
Asphalt shingles are sold by the bundle, with roughly three bundles covering one “square” (100 sq ft) on a standard-weight product — check the wrapper for your specific product’s coverage rather than assuming three bundles per square. Standing seam metal is typically sold and estimated by panel; select the Metal panel shingle type above to switch the Shingles quantity to a panel count (roof area divided by your panel’s covered area, editable) instead of bundles — panels are commonly custom-cut to the rafter length, so confirm exact panel layout and length with your supplier.
Low-slope roofs need extra attention: most asphalt shingle manufacturers set a minimum reference pitch around 2:12 (with special underlayment below 4:12), and standing seam metal is commonly referenced around 3:12 minimum. This calculator flags a warning when your entered pitch is below those general reference points, but manufacturer installation instructions and local code always take precedence over a general reference.
FAQ
Do I have to re-enter roof area for shingles and sheathing?
No. Roof length, rise/run/pitch, and overhang are entered once and the resulting roof area feeds both Shingles and Sheathing automatically.
Can I still fine-tune just the shingles or sheathing numbers?
Yes. Flip a calculator to "Manual entry" to edit its inputs directly — for example if you're buying panels in a size the master inputs don't cover — without changing the roof geometry or the other calculators.
Why does a gable roof need this run twice?
This page calculates one roof plane at a time, matching the standalone Roof calculator — rafter count, roof area, shingle bundles, and sheathing sheets are all sized for that single plane. For a gable roof, run it once per plane (they're usually identical) and double all four totals, or use the Shed/Barn template if you're estimating a full gable building in one pass (it applies the plane-count multiplier for you).
What does the pitch warning mean?
It's a general reference check against common manufacturer minimums for the covering material you selected, not a code determination. Always verify against your product's installation instructions and local code.
Disclaimer
Material estimate and general reference only. Verify local code, structural requirements, and manufacturer installation instructions before ordering or starting work.