Shed Lumber Calculator

How the shed lumber calculator works

This calculator gives the first numbers you need for a small timber-framed shed: how many wall studs, and how much sheet material for the walls, roof and floor. The stud count is the wall perimeter divided by the stud spacing, rounded up, plus four for the corners. The wall area is the perimeter times the eaves height, the roof area is the floor footprint times 1.15, and the floor area is length times width. Each quantity is multiplied by the price you enter.

Run the US defaults by hand and you get the same figures as the tool. An 8 × 6 ft shed has a 28 ft perimeter, or 336 in; 336 ÷ 16 = 21, plus 4 is 25 studs, which cost $200 at $8 each. The walls are 28 × 7 = 196 ft², the roof is 48 × 1.15 = 55.2 ft², the floor is 48 ft², and 299.2 ft² at $1.20 comes to $359.04. The metric defaults follow the same path: a 2.4 × 1.8 m shed has an 8.4 m perimeter, 8,400 ÷ 400 = 21, so 25 studs, and 16.8 + 4.97 + 4.32 = 26.09 m² of sheet costs £260.88 at £10 per m².

Timber and sheet wastage

The tool doesn't add a wastage percentage, and two of its shortcuts matter when you order. Sheet cost is worked out by area, but you buy whole sheets. A 4 × 8 ft sheet is 32 ft², so $1.20 per ft² is a $38.40 sheet. The default walls need 196 ÷ 32 = 6.1 sheets, which means 7; the roof needs 1.7, so 2; the floor needs 1.5, so 2. That's 11 sheets and $422.40, not $359.04. In metric, a 2,440 × 1,220 mm sheet is 2.98 m², or £29.77 at £10 per m², and the same rounding gives 6 + 2 + 2 = 10 sheets for £297.68. After that, add 10 to 15% for offcuts around doors, windows and the roof edge.

The stud count is a floor, not a take-off. Framing each wall separately usually needs more studs than a single loop around the perimeter. On the default shed, each 8 ft wall at 16 in centres has 6 spaces and 7 studs. The 6 ft end walls sit between them, so they are 72 − 7 = 65 in long between the 3-1/2 in side walls; 65 ÷ 16 = 4.06, which rounds up to 5 spaces and 6 studs. That's 26 before any extra corner studs, against the tool's 25. Each door or window also needs a king stud and a jack stud on both sides plus short cripples above the header, so add two to four studs per opening.

What this tool does not do

It doesn't count plates, floor joists, rafters, noggins or blocking, and it doesn't size any of them. Plates are easy to add by hand: a bottom plate and a doubled top plate make three runs of the perimeter, so the default shed needs 3 × 28 = 84 ft, or ten and a half 8 ft lengths, which you round up to 11. The metric default is 3 × 8.4 = 25.2 m, the same eleven 2.4 m lengths. It also treats the eaves height as the stud length. With a bottom plate and two top plates of 1-1/2 in stock, a 7 ft wall takes studs 84 − 4.5 = 79.5 in long; with 38 mm plates, a 2,000 mm wall takes studs of 1,886 mm.

The roof figure needs the most care. Multiplying by 1.15 is the slope factor for a pitch of about 30° (roughly 7 in 12), with no overhang. A shallow pent roof at 10° only needs a factor of 1.02, and a 45° roof needs 1.41. Overhangs aren't included either: 6 in at each gable end and 12 in at each eave turn the default 8 × 6 ft roof into 9 × 8 = 72 ft² of plan, or 82.8 ft² at 1.15, not 55.2. In metric, 150 mm and 300 mm overhangs make it 2.7 × 2.4 = 6.48 m², or 7.45 m². The wall area leaves out the two gable triangles, which add about 10.4 ft² on a 6 ft wide shed at 30° (0.94 m² on a 1.8 m shed), and it doesn't subtract door or window openings.

On-site considerations for shed lumber

Check the grade stamp on every piece. In North America, framing lumber is graded under rules such as NLGA or WCLIB, and Stud or No. 2 grade is the usual choice for shed walls. In the UK and Europe, look for a strength class such as C16 or C24. Keep the floor frame off the ground. Skids, bearers and floor joists that sit on or close to the soil need timber treated for ground contact: UC4A under the US AWPA system, or Use Class 4 in the UK and Europe. Wall framing that stays dry can be ordinary kiln-dried timber.

Leave a small gap between sheathing panels. APA's builder tip on panel spacing recommends 1/8 in (about 3 mm) at panel edges and ends so the boards can swell without buckling. That gap is one reason to round sheet quantities up rather than trying to make the last sheet stretch.

Codes and compliance

Small sheds are often exempt from building permits or building regulations, but the limits depend on where you live, and they cover floor area, height, distance from the boundary and use. In England, the Planning Portal's outbuildings guidance sets out the permitted development limits, including a maximum height of 2.5 m for an outbuilding within 2 m of a boundary. That limit is the whole building, ridge included, so a shed close to the fence needs its eaves lower still. In the US, the American Wood Council's Wood Frame Construction Manual is referenced by the 2024 International Residential Code, but your city or county decides which edition applies and whether a shed of your size needs a permit. If the shed will carry snow, sit on a slope or be used as a room, get the framing checked by your building department or a structural engineer before you order.

Before you order

Turn the tool's figures into a cutting list. Take the studs, then add corner studs and two to four per opening. Add three runs of plate, the floor joists and the rafters, and round the sheet materials up to whole sheets. Buy studs a little longer than the wall height so each one can be trimmed square, and check that sheet sizes at your supplier match the ones you planned with, since 4 × 8 ft and 2,440 × 1,220 mm are close but not the same. Sight along the studs before you accept a delivery and send back any that are badly bowed or twisted.

Adjusting the defaults

The US side opens at 8 × 6 ft, 7 ft eaves, 16 in centres, $8 a stud and $1.20 per ft² of sheet. The metric side opens at 2.4 × 1.8 m, 2 m eaves, 400 mm centres, 6 a stud and 10 per m², shown in pounds in the UK because the currency symbol follows your browser's region. Treat them as placeholders. If your supplier prices sheets individually, divide the sheet price by its area: a $38.40 sheet of 32 ft² is $1.20 per ft², and a £29.77 sheet of 2.98 m² is £10 per m². Enter 24 in or 600 mm centres only if your cladding and sheathing are rated for that span.

Using this shed lumber calculator alongside other BuildMetricLab tools

Use this calculator for the wall studs and the sheet areas, then add the pieces it leaves out. The nail and screw calculator covers fixings, and the I-joist calculator helps if you frame a larger floor with engineered joists. Everything runs in your browser, nothing you type is sent anywhere, and the formula is on the page so you can check every step, as the worked examples above do.