Shed Material Calculator

Shed Material formula

Studs = (Perimeter (in) / spacing + 1 + 4 corners x 3 + openings x 4) x 1.1
Plates (ft) = 3 x perimeter;  Joists = Length (in) / 16 + 1, each Width, plus 2 rim joists
Sheets = (floor area + perimeter x height + roof area) / 32 x 1.1
Rafter = Width / 2 x pitch factor + 1 ft;  Roof area = 2 x Length x rafter;  Bundles = Roof area / 100 x 3 x 1.1

Worked example

A 16 x 12 ft shed with 8 ft walls, a 6/12 gable roof, studs 24 in on center, one door and two windows. Perimeter = 56 ft. Studs: 56 x 12 / 24 = 28, plus 1 = 29 field studs, plus 12 for corners and 12 for three openings = 53; with 10% waste, 59 studs. Plates: 3 x 56 = 168 ft. Joists: 16 x 12 / 16 = 12, plus 1 = 13 joists 12 ft long plus 32 ft of rim = 188 ft.

Sheathing: floor 192 / 32 x 1.1 = 6.6, so 7 sheets; walls 56 x 8 / 32 x 1.1 = 15.4, so 16. The 6/12 pitch factor is 1.118, so rafters are 6 x 1.118 + 1 = 7.71 ft and the roof is 2 x 16 x 7.71 = 246.7 sq ft: 246.7 / 32 x 1.1 = 8.5, so 9 sheets, and 246.7 / 100 x 3 x 1.1 = 8.1, so 9 bundles. Rafters: 2 x (16 x 12 / 24 + 1) = 18.

Quick reference

How to estimate shed materials

Treat the four walls as one long wall equal to the perimeter. Divide by the stud spacing, add one, then add three studs for each of the four corners and four for every door and window. Plates are three times the perimeter: a bottom plate and a double top plate. Order 10 percent extra on everything; sheds are built from the cheaper grades and a few boards in every bundle are too crooked to use.

Sheathing is counted by area: floor, walls (perimeter times height) and both roof planes, each divided by the 32 sq ft in a sheet. The gable triangles are small and come out of the waste allowance.

Floor, roof and what is not included

A shed floor on skids or blocks uses treated 2x6 joists 16 in on center spanning the width, boxed by rim joists, under 3/4 in tongue and groove plywood. For the roof, the rafter length is half the width times the pitch factor plus a foot of overhang; a 4/12 pitch sheds water fine and keeps rafters short, while 6/12 gives loft storage.

This estimate covers framing, sheathing and shingles only. Siding, corner and door trim, the door and window units, roofing underlayment, drip edge, ridge cap, nails and joist hangers are extra, and together they are often as much as the framing. Check setbacks and the permit threshold with the local building department before ordering.

Key facts

• The IRC exempts detached accessory buildings of 200 sq ft or less from a building permit, but zoning setbacks still apply and many cities set a lower limit.
• A bundle of 3-tab shingles covers about 33 sq ft, so three bundles make one roofing square of 100 sq ft.
• A 4 x 8 sheet covers 32 sq ft; 7/16 in OSB is standard for shed walls and roofs, and 3/4 in tongue and groove plywood for floors on joists 16 in on center.
• The rafter pitch factor is 1.054 for 4/12, 1.118 for 6/12 and 1.014 for 2/12.
• Asphalt shingles need at least a 2/12 pitch, and pitches under 4/12 require two layers of underlayment.

Frequently asked questions

Sources and references

• •Chapter 6 Wall Construction, 2021 IRC (stud spacing and fastening) (ICC)
• •Chapter 1 Scope and Administration, 2021 IRC (R105.2 work exempt from permit) (ICC)
• •Engineered Wood Construction Guide (Form E30) (APA The Engineered Wood Association)
• •Oakridge shingles product page (3 bundles per square) (Owens Corning)