Shed calculator
A count at the spacing and sizes you choose. It does not size any member or say what it will carry, and it knows nothing of your local permit rules — check both before you buy.
Type the shed’s footprint, wall height and roof pitch, and the spacing from your plans. You get the floor joists and floor sheets, every stud and plate, the wall sheathing including the two gable triangles, and the rafters, ridge and roof sheets — as one list you can print or send to the lumber yard.
Worked example
An 8 × 10 ft shed, 8 ft walls, a 6-in-12 roof, studs and joists at 16 in, rafters at 24 in, 6 in overhangs, one door, 4 × 8 sheets and 10% waste.
Floor: joists across the 8 ft, counted along the 10: 120 ÷ 16 = 7.5 → 8 bays, 9 joists of 8 ft and two 10 ft rims. 80 ft² × 1.1 ÷ 32 = 2.75 → 3 sheets. Walls: 9 + 9 + 7 + 7 = 32 studs, + 4 corners + 4 for the door = 40 studs. Plates: three runs on each wall, six of 10 ft and six of 8 ft (108 ft). The gables rise 4 × 6/12 = 2 ft, so the walls are 36 × 8 + 8 × 2 = 304 ft², × 1.1 ÷ 32 = 10.45 → 11 sheets. Roof: the ridge is 10 + 2 × ½ = 11 ft; 132 ÷ 24 = 5.5 → 6 bays, 7 pairs, 14 rafters of (4 + ½) × 1.118 = 5′ 3/8″ each. Roof area 2 × 11 × 5.03 = 110.7 ft² → × 1.1 ÷ 32 = 3.8 → 4 sheets.
In metric: 2.4 × 3.0 m, 2.4 m walls, 26.6° (the same 1 in 2), 400 mm studs and joists, 600 mm rafters, 150 mm overhangs, 1200 × 2400 sheets: 9 joists, 40 studs, 11 wall sheets, 14 rafters of 1,509 mm and 4 roof sheets.
Try one
Quick referencefor a shed
- Members
- length ÷ spacing, rounded up, + 1 — studs, joists, rafter pairs
- Gable rise
- half the width × pitch ÷ 12 · two gables = width × rise
- Rafter
- (half the width + eave) × √(1 + (pitch ÷ 12)²) · 6 in 12 → × 1.118
- Sheets
- area × (1 + waste) ÷ sheet · 4 × 8 = 32 ft² · 1200 × 2400 = 2.88 m²
- Plates
- bottom + top(s) on every wall: 3 × the perimeter for double top plates
The formula
studs = Σ(⌈wall ÷ spacing⌉ + 1) + extras · rafter = (W/2 + eave) × √(1 + pitch²) · sheets = ⌈area × (1 + waste) ÷ sheet⌉
Questions
- How many studs for a shed?
- Lay out each wall on its own length at your spacing — the length divided by the spacing, rounded up, plus one — then add the extras: the corner studs and a king and a jack each side of every door and window. An 8 × 10 ft shed at 16 in centres is 9 + 9 + 7 + 7 = 32 layout studs; one extra at each corner and four for a door makes 40.
- Is the rafter length the length to cut?
- It is the line length along the slope from the centre of the ridge out to the end of the eave overhang. Take half the ridge board’s thickness off, measured level, at the top, and mark the seat cut where the rafter crosses the wall. The rafter length calculator does the cuts for one rafter in detail.
- Why count the end walls on their full length?
- The end walls actually fit between the long walls, so the true layout is a stud width shorter at each end. Counting the full length can add a stud; it never leaves you one short. On a shed that is the right side to err on.
- Does this tell me what size lumber to use?
- No. Joist, rafter and header sizes, spans, and whether you need a permit come from your plans, your span table and your local rules. The page counts and measures the members at the spacing you give it; it does not say what they will carry.
- Does the sheathing count take off the door?
- No — doors and windows are cut out of whole sheets, and the offcuts rarely cover anything else. The count is the wall area (plus the two gable triangles) with your waste allowance, rounded up to whole sheets.
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