Shed Size Calculator

Understanding shed sizes in Australia

Working out the size you need, not the size you can afford

Most people approach a shed backwards. They pick a price, get the footprint that price buys, then discover it does not hold what they own. The better sequence is to add up what has to go inside, add the access space around each item, then find the smallest footprint that satisfies that and price it. As base figures, a single car needs a bay about 3m wide by 6m deep to be genuinely usable, two cars need about 6m by 6m, a ride-on mower and garden gear needs roughly 3m by 3m, a standard 6m caravan needs a 3.5m wide by 8m deep bay with 3.2m of clearance, and a trailer boat on a tandem needs 3m by 7.5m. A workbench with clearance to work at it takes a strip 2.4m deep by however wide the bench is, and a machinery workshop with a table saw, drop saw and mobile tool chests needs 4m by 4m as a working minimum.

Depth is the dimension that matters most

If you take one rule from this page, it is that depth is far more important than width, because depth is the dimension you cannot work around. A car is about 4.8m long and needs room to open the door and walk past, so a 6m deep bay is comfortable, 5.5m is workable and 5m means climbing out sideways every time and never storing anything against the back wall. Two sheds of identical area behave completely differently, and a 6m by 6m double garage is a usable space while a 9m by 4m shed of the same 36m² will not take a car plus anything else. Set the depth from the longest item you need to house plus a metre, and only then decide how wide the shed needs to be.

What each size costs in 2026

Once you know the footprint you can price it. A 3m by 3m garden shed kit is $900 to $2,500 supplied, or $2,500 to $5,000 with a slab and installation. A 6m by 3m single garage shed is $4,500 to $9,000 supplied and installed on a slab. A 6m by 6m double garage runs $9,000 to $18,000. A 9m by 6m workshop is $15,000 to $28,000, and a large 12m by 9m rural shed is $28,000 to $55,000 depending on wall height and wind region. Roughly a third of a completed shed budget is the slab, which runs $80 to $150 per square metre for a standard domestic slab and more where the engineering calls for a thickened edge or heavier reinforcement under a hoist or racking.

Wall height, mezzanines and cheap vertical space

Wall height is the most underrated lever on a suburban block. Standard domestic sheds are 2.4m at the wall. Stepping to 3.0m costs roughly 20 percent more, and it buys three things. It allows a mezzanine storage platform over part of the footprint, which effectively adds floor area without adding to the area figure your council assesses. It allows a car hoist, which doubles vehicle capacity on the same slab. And it allows racking to the underside of the roof rather than to shoulder height. On a block where footprint is constrained by setbacks or by the exempt development area cap, buying height is by far the cheapest way to get more usable space. The trade off is that taller walls carry more wind load, so the frame, footings and bracing all step up, and the height itself may push you over a council height threshold.

Council approval and where the thresholds sit

Small sheds are usually exempt or complying development and need no approval. The limits vary by state and by local government area, but the common pattern is a floor area cap somewhere between 10m² and 20m², a wall height limit of 2.4m to 3m, an overall height limit around 3m to 4.5m, and a setback from side and rear boundaries of at least 900mm. A 3m by 3m garden shed at 9m² clears everywhere. A 6m by 3m single garage at 18m² is marginal and depends entirely on your LGA. A 6m by 6m double at 36m², or anything with a 3m wall, is over the line almost everywhere and needs either a complying development certificate or a full development application, plus engineering certification for the wind region. Application fees are typically $600 to $2,500 and the process takes four to twelve weeks, so it is worth a phone call to the council duty planner before you lock in dimensions.

Site works, slope and the costs that sit outside the quote

A shed quote almost always prices the shed and often the slab, and rarely everything else. On a level, open block with truck access the extras are modest. On a sloping site they can be enormous, because you need cut and fill to create a level pad, usually a retaining wall on the high side, and deeper footings on the fill side, which together commonly add $4,000 to $15,000. A retaining wall over about a metre high needs engineering and its own approval. Other items that sit outside a typical shed quote are a driveway or hardstand approach at $60 to $120 per square metre, stormwater connection from the shed gutters to the legal point of discharge, and power, which as licensed electrical work runs $1,200 to $3,500 for a submain, board and a few circuits. Budget these separately rather than assuming a headline shed price is the finished number.

Sizing for what you will own in five years

The last consideration is time. Sheds are not extendable in any practical sense. Bolting a lean-to onto an existing frame is possible but the result is rarely as good or as cheap as building the right size once, and it usually triggers a fresh approval because it changes the total floor area. People consistently underestimate future needs, because a shed generates its own demand: once the space exists, the boat, the trailer, the second project car and the garden furniture find their way into it. The practical advice is to size for what you expect to store in five years, then check that footprint against your council's thresholds and your budget, and if you have to compromise, compromise on width and on finish rather than on depth or height, because those two are the dimensions that decide whether the space works at all.