Shed Cost Calculator — material take-off and itemised build cost

Nobody can tell you what a shed costs. What anyone can tell you is how much material a shed of a given size contains, and that is a fixed, checkable number: so many square feet of floor, so many lineal feet of framing, so much wall to clad and so much roof to cover. This shed cost calculator produces that take-off from four dimensions, then multiplies it by unit rates that you supply from your own supplier.

Arb Digital builds free estimating tools for trades and self-builders, and this one is deliberately split down the middle. The left-hand half — the geometry and the quantities — is arithmetic and it is the same everywhere. The right-hand half — the money — is local, volatile and specific to your merchant, which is why this page holds no price list of any kind.

What This Shed Cost Calculator Does

Enter a footprint, a wall height, a roof pitch, a framing spacing and an overhang, and it works out the floor area, the total lineal feet of framing lumber in the floor, walls and roof, the wall area including the gable triangles, and the true sloping roof area including the overhang. Those four quantities are the take-off, and they are correct regardless of what anything costs.

Then it applies your unit rates: a foundation rate per square foot of floor, a lumber rate per lineal foot, a combined sheathing-and-siding rate per square foot of wall, a combined deck-and-covering rate per square foot of roof, and a lump sum for doors, windows, fasteners and hardware. The bars show how the money splits between foundation, framing, walls and roof, which is where the interesting decisions live.

The hero figure stays blank until you enter at least one rate, because a total of zero would be a false answer rather than a helpful one. The quantities populate immediately either way.

How to Use It

1. Enter the footprint. Length is the direction the ridge runs; width is the direction the roof slopes. Swapping them changes the gable area and the rafter length, so it matters.
2. Set the wall height and pitch. Pitch is rise per twelve of run. If you only have the angle in degrees, convert it first with the roof pitch calculator.
3. Choose the framing spacing and overhang. Both are inputs. Spacing affects the lumber count directly and is a design decision for your building department, not for this page.
4. Get your unit rates. Ask a merchant for a price per lineal foot on the framing size you intend to use, and per square foot or per sheet on the cladding and roofing. Convert per-sheet prices by dividing by 32 for a standard four-by-eight sheet.
5. Add a lump sum and a contingency. Doors, windows and hardware are too variable to model, and ten per cent contingency on a first build is not pessimistic.

The Formula and How It Is Calculated

Floor area is length × width. Wall area is the perimeter, 2 × (length + width), multiplied by the wall height, plus the two gable triangles. Each gable is half the width times the rise, where the rise is half the width multiplied by pitch ÷ 12.

Roof area is the horizontal plan area including the overhang on all four sides, multiplied by the slope factor √(1 + (pitch ÷ 12)²). A 4/12 roof has a slope factor of 1.0541, so a nominally flat 168 square foot plan becomes 177 square feet of actual roof surface — the single most commonly missed six per cent in shed estimating.

The framing take-off adds four groups. Studs: the perimeter divided by the spacing, rounded up, plus eight for corners and openings, each one the wall height. Plates: three runs of the perimeter, one sole plate and a double top plate. Floor framing: joists at the same spacing spanning the width, plus two rim joists along the length. Roof framing: rafters at the same spacing on both slopes, each running from ridge to eave including the overhang along the slope, plus a ridge board.

Worked example: a 12 × 10 shed with 8 ft walls, a 4/12 roof, 16 in spacing and a 12 in overhang. Floor area is 120 sq ft. The perimeter is 44 ft, so wall area is 352 sq ft; the rise is 5 × 0.3333 = 1.667 ft, so the two gables add 2 × ½ × 10 × 1.667 = 16.7 sq ft, giving 368.7 sq ft of wall. The roof plan with a foot of overhang all round is 14 × 12 = 168 sq ft, times 1.0541 = 177.1 sq ft of roof. Framing comes to 722 lineal feet: 41 studs at 8 ft is 328, three runs of plate is 132, ten joists plus rims is 124, and twenty rafters at 6.32 ft plus a 12 ft ridge is 138. Enter a rate against each of those and you have a costed take-off rather than a guess.

Why This Page Publishes No Prices

Any page that prints "a 10 × 12 shed costs X" is wrong somewhere the day it is published and wrong everywhere within a year. Lumber prices are famously volatile, sheet goods track a different market again, and the same nominal item can differ by a third between two merchants in the same town depending on grade, treatment and whether you are buying a unit or a piece. Regional differences on top of that are larger still.

The honest structure is the one used here: publish the quantities, which do not change, and take the rates from the person who is actually going to sell you the material. It also makes the tool useful outside one country, since a rate per lineal foot works identically in any currency. The same reasoning governs every cost tool Arb Digital publishes.

Where the Money Actually Goes

Run the bars on a few different designs and a pattern appears. On a small shed the foundation and the roof are disproportionately expensive relative to the floor area, because both scale with an area that includes the overhang and neither gets cheaper as the building shrinks. Framing scales with perimeter and height rather than area, which is why a long thin shed costs materially more than a square one of the same floor area — a 6 × 20 shed has 52 feet of perimeter against 44 for a 10 × 12, for the same 120 square feet inside.

Wall height is the other quiet cost driver. Going from 7 ft to 8 ft walls on the example above adds 44 square feet of cladding and 41 feet of stud length, for no extra floor area at all. Whether that is worth it depends entirely on whether you need the headroom or the shelf space, but it is worth seeing the number before deciding.

What the Estimate Deliberately Leaves Out

This is a material take-off, not a build budget. It contains no labour, no plant hire, no delivery, no waste disposal, no permit fee and no groundwork beyond the foundation area you priced. It assumes a simple gable roof on a rectangular plan with no dormers, no porch and no lean-to. It makes no allowance for site slope, which can turn a straightforward pad into a retaining exercise.

It also says nothing about whether you may build the thing. Permit thresholds, setback distances from boundaries, height limits and maximum floor areas for accessory structures vary by jurisdiction, and in many places a shed above a certain size needs a permit and an inspection. The model residential provisions are published by the International Code Council as the International Residential Code, but they are adopted with local amendments and your building department has the final word. The National Association of Home Builders publishes background on residential construction practice if you want wider context.

Sanity-Checking a Quote Against the Take-Off

The most valuable use of this page is not producing a number of your own but interrogating someone else's. If a kit or a builder quotes a price, divide it by the floor area to get a rate per square foot, then compare the material split against the bars here. A quote where the roof line looks light for the overhang specified, or where the framing line implies a spacing wider than you were told, is worth a question.

For the individual trades, our other calculators go deeper than the summary lines here: the siding calculator handles cladding coverage and courses, the roofing calculator converts roof area into squares, bundles and underlayment rolls, the concrete calculator sizes a slab, and the board foot calculator prices lumber by section rather than by lineal foot.

Common Mistakes to Avoid

• Using the roof plan area as the roof area. The slope factor adds five per cent at 4/12 and twelve per cent at 6/12, and the overhang adds more again.
• Forgetting the gable triangles. They are small individually but they need cladding, framing and trim like any other wall.
• Pricing sheet goods per sheet and entering it per square foot. Divide by 32 for a standard four-by-eight sheet before entering the rate.
• Treating the total as a build budget. There is no labour, delivery, waste disposal or permit cost in this figure, and on many projects those together exceed the materials.
• Assuming the shed needs no permission. Size thresholds, setbacks and height limits vary by jurisdiction, and finding out afterwards is expensive.

Related Free Tools From Arb Digital

Convert and check the slope with the roof pitch calculator, take off the covering with the roofing calculator and the cladding with the siding calculator, size a base with the concrete calculator, price timber precisely with the board foot calculator, and build a deck alongside it with the decking calculator. Everything else is in the free tools hub.

Frequently Asked Questions

This tool produces a material take-off and multiplies it by unit rates you enter yourself. It publishes no prices, no material sizes and no span or spacing recommendations, it performs no structural check, and it excludes labour, delivery, waste disposal and permit costs. Confirm quantities and rates with your supplier, and confirm permit requirements, setbacks and construction standards with the building department having jurisdiction over your site.