Shed roof material estimator

Shed Roof Calculator

Estimate shed roof rafter length, roof deck area, sheathing sheets, rafter rows, waste, and rough material cost from shed length, roof run, pitch, and roof-plane count. Use it for shed roof takeoffs before checking spans, loads, and local code.

Units

Shed length along roof (ft)Horizontal roof run (ft)Eave overhang (ft)Roof pitch (in / 12)Roof planes Rafter spacing (in OC)Sheet coverage (ft²)Waste / cuts (%)Cost per sheet ($)Cost per rafter ($)

Rafter length

Sheets to buy

Order area

Rough cost

Shed roof counts are not structural design

This calculator estimates geometry and material counts only. Rafter size, snow and wind loads, roof diaphragm, ties, fasteners, ventilation, waterproofing, and local code must be checked before building.

Android App

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Rafter Length Calculator

Check common rafter geometry from run and pitch.

Roof Sheathing Calculator

Estimate roof deck sheets for larger roof planes.

Roof Underlayment Calculator

Estimate roll coverage after roof area is known.

View all

Shed roof formula

Rise = (roof run + overhang) × pitch ÷ 12

Rafter length = sqrt((run + overhang)² + rise²)

Measured roof area = rafter length × shed length × roof planes

Sheets = measured area × (1 + waste %) ÷ sheet coverage

Sample takeoff

A 12 ft long shed roof with a 8 ft run, 1 ft overhang, 4/12 pitch, one roof plane, and 10% waste needs about a 9.49 ft rafter line and four 4×8 sheathing sheets.A 3.6 m long shed roof with a 2.4 m run, 0.3 m overhang, 4/12 pitch, one roof plane, and 10% waste needs about a 2.85 m rafter line and four 2.88 m² sheets.

Shed Roof Calculator FAQ

How do I calculate a shed roof rafter length?+

Add the overhang to the horizontal run, calculate rise from pitch, then use the Pythagorean theorem for the rafter line length.Add the overhang to the horizontal run, calculate rise from pitch, then use the Pythagorean theorem for the rafter line length.

Can I use this for a gable shed roof?+

Yes for material area if both roof planes are similar. Enter two roof planes and use the run for one side of the roof.Yes for material area if both roof planes are similar. Enter two roof planes and use the run for one side of the roof.

Does this choose rafter size?+

No. It counts material and geometry. Use span tables, product data, or an engineer for rafter sizing and structural approval.No. It counts material and geometry. Use span tables, product data, or an engineer for rafter sizing and structural approval.