Shed Roof Calculator

Calculate roofing materials, framing lumber, and cost for single-slope shed roofs

Get a fast material estimate from basic dimensions

Quick presets

ft
ft

Estimated Materials

0 bundles

0.0 squares • 0 sq ft

PRO

Professional Calculator

Extended parameters for precise calculations

sq ft

Estimated Materials

60 bundles

Roof Area

1,792 sq ft

Squares

17.9

Detailed Breakdown

Roof Area1,792 sq ft
With Waste1,971 sq ft
Roofing Squares17.9
Bundles60
How to Use This Calculator
Enter your shed dimensions on the Quick Estimate tab — length (along the eave), width (rafter span), and desired pitch. Select shingles or metal panels and add your eave overhang. The calculator instantly outputs the true sloped roof area, rafter length, and a basic material count.

For a detailed material list, switch to the Material Estimate tab. Choose your exact roofing product (architectural shingles, 3-tab, corrugated, or standing seam), waste factor, and whether you need underlayment and drip edge. You will get bundle counts, panel counts, underlayment rolls, and drip edge pieces.

The Framing tab helps you plan the structural side. Enter your span, pitch, and preferred rafter spacing (16" OC is standard). The calculator recommends a rafter lumber size, shows total rafter count, and notes whether you need a ledger board or tall-wall framing. Use the preset scenarios to see common shed sizes at a glance.

The Formula
Pitch Factor = sqrt(1 + (rise/12)^2) (e.g., 4/12 pitch factor = 1.054) Rafter Length = Shed Width x Pitch Factor + Overhang Roof Area = Shed Length x Rafter Length Rafter Count = (Shed Length / Rafter Spacing) + 1 Shingle Bundles = Roof Area / 33.3 x (1 + Waste%) Metal Panels = Roof Area / (Panel Width x Panel Length) x (1 + Waste%) High-Wall Height = Low-Wall Height + (Shed Width x Rise/12)
Example Calculation
For a 12x16 workshop with 4/12 pitch and metal panels:
• Pitch factor: sqrt(1 + (4/12)^2) = 1.054
• Rafter length: 12 x 1.054 + 1 ft overhang = 13.65 ft (buy 14-ft 2x6)
• Roof area: 16 x 13.65 = 218 sq ft
• Metal panels (3 ft wide, 14 ft long): 218 / 42 x 1.10 = 6 panels
• Rafters: (16 / 1.33) + 1 = 13 rafters at 16" OC
• Ledger board: 1 x 16 ft pressure-treated 2x8
• Sheathing: 218 / 32 = 7 sheets of 4x8 plywood
• Estimated material cost: $1,200-1,800

Frequently Asked Questions

What is the minimum pitch for a shed roof?
The minimum pitch depends on roofing material. Asphalt shingles require at least 3/12 (14 degrees). Metal panels can go as low as 1/12 (5 degrees) with proper sealant at overlaps. A 4/12 pitch is the most common for sheds because it sheds water well, looks proportional, and stays easy to build.
How long should rafters be for a shed roof?
Rafter length equals the hypotenuse of the pitch triangle plus overhang. For a 10-ft span at 4/12 pitch: rafter length = 10 / cos(18.4 degrees) = 10.54 ft, plus a 1-ft overhang = 11.54 ft. Buy 12-ft lumber and cut to fit. Use our calculator for exact dimensions including birdsmouth cuts.
Do I need a building permit for a shed roof?
In most US jurisdictions, sheds under 120-200 sq ft (varies by locality) do not require a building permit. Larger sheds, attached lean-tos, and sheds with electrical or plumbing almost always need a permit. Check your local building department — some HOAs have additional restrictions on materials and height.
Should I use shingles or metal on a shed roof?
Metal panels are the better choice for most sheds. They are lighter (1 lb/sq ft vs 2-4 lb/sq ft for shingles), install faster with fewer pieces, last 40-60 years, and perform well at low pitches. Shingles make sense if you want to match an existing house roof or prefer the lower upfront cost on small projects. For a 10x12 shed, the material cost difference is only about $100-200.
What size lumber do I need for shed rafters?
For most residential sheds: 2x4 rafters at 16" OC span up to about 7 feet, 2x6 rafters span up to 11 feet, and 2x8 rafters span up to 15 feet. These assume SPF #2 lumber, 20 psf live load, and 10 psf dead load. Snow-load regions may require upsizing. Always verify with local span tables or an engineer for spans over 12 feet.

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