Shed Roof Calculator: Single-Slope Roof Rise, Rafters and Materials (2026)
One slope, one high wall, one low wall. Here's how to size a shed roof and buy the right materials the first time.
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A shed roof (also called a lean-to or skillion roof) slopes in one direction. It's the go-to for backyard sheds, porch additions and modern homes — and it's the simplest roof you can frame.
The shed roof formula
- Rise = width × pitch ÷ 12 — this is how much taller the high wall is
- Rafter length = √(width² + rise²), plus overhang
- Area = rafter length × shed length, plus 10% waste
- Sheathing sheets = area ÷ 32 (one 4x8 sheet)
Example: a 10 × 12 shed at 3/12 with 6-inch overhangs. Rise ≈ 2.75 ft, rafter ≈ 11.3 ft, area ≈ 150 sq ft — five sheets of OSB and five bundles of shingles.
Minimum pitch matters
- Asphalt shingles: 2/12 minimum (4/12 without special underlayment)
- Metal panels: as low as 1/2 to 1/12 depending on the panel
- Rolled roofing: 1/12 to 2/12 — cheap, but shorter lived
Below 2/12, skip shingles. Metal or rolled roofing will save you from leaks.
Enter shed size and pitch to get rise, rafters, sheets and cost.
Open the Shed Roof CalculatorFAQs
How much does it cost to roof a shed?
A 10×12 shed usually costs $350–$900 in materials for DIY, or $900–$2,000 installed, depending on material and region.
What's the best pitch for a shed roof?
3/12 to 4/12 is a good balance of drainage, headroom and simple framing.
Can I use a shed roof on a house?
Yes — it's common on modern homes and additions. Use metal or membrane roofing on low slopes.
Written by Javed Niamat
Javed Niamat is a home renovation cost analyst and the founder of RenoCalc Hub. He tracks US remodeling labor rates, material pricing and contractor bids across all 50 states, and builds the free calculators behind every guide on this site.
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