Free shed size calculator. Enter large and medium stored items to estimate the floor area your shed needs in square feet and metres.
Your results will appear here.
Enter your values and press Calculate.
Each large item, such as a ride on mower or large workbench, is allowed 25 square feet, and each medium item, such as a bicycle or tool chest, is allowed 8 square feet. The total is the floor area before walkways, so round up to the next standard shed size.
This calculator estimates shed floor area from item counts: each large item, such as a ride on mower or large workbench, is allowed 25 square feet, and each medium item, such as a bicycle or tool chest, is allowed 8 square feet. Two large items and five medium items need 50 plus 40, which is 90 square feet, or about 8.4 square metres. That total is the floor area before walkways, so round up to the next standard shed size and leave room for a walkway down the middle, or the shed will be hard to use.
This shed size chart lists the sizes shops actually sell. A 6 by 8 foot shed is 48 square feet. An 8 by 8 foot shed is 64 square feet. An 8 by 10 foot shed is 80 square feet. A 10 by 10 foot shed is 100 square feet. A 10 by 12 foot shed is 120 square feet. A 12 by 16 foot shed is 192 square feet. A 12 by 20 foot shed is 240 square feet. A 16 by 24 foot shed is 384 square feet. Small sheds are under 100 square feet, medium sheds are 100 to 200 square feet, large sheds are 200 to 400 square feet, and garage class sheds are over 400 square feet.
Tool storage alone fits 6 by 8 to 8 by 10 feet. A shed size for riding mower work is 10 by 10 or 10 by 12 feet, with door width checked separately. A motorcycle fits 10 by 12 to 12 by 16 feet. A shed size for workshop use is 12 by 16 feet or larger, with 16 by 20 feet or larger for a serious workshop. A shed size for home office use is 10 by 12 to 12 by 20 feet. A home gym fits 10 by 12 to 12 by 20 feet. A single car needs 12 by 20 to 14 by 24 feet, and farm equipment needs 20 by 30 feet and up.
A shed should fit its yard, not just its contents. A small yard of a quarter acre and under suits 8 by 10 feet or smaller. A medium yard of half an acre and under suits 10 by 12 feet or smaller. A large yard of an acre and above suits 12 by 12 feet or larger. Leave at least 3 feet clearance from fencing and trees for access and maintenance, and check setbacks before buying, because a shed that fits the contents but breaks a setback rule cannot be placed where you planned.
Clearance matters as much as floor area. Allow 3 to 4 feet on the access side and 1 to 2 feet on the remaining sides, so items can be moved in and out. Shed door width matters too: a standard 36 inch door suits boxes and hand tools, but bikes, mowers, and bulky equipment need a double or wider door, so measure the widest item and the door swing. Shed wall height is commonly 7 to 8 feet, and 8 foot walls suit workshop use better, because they allow taller shelving and easier standing work.
Shed foundation scales with size. Small sheds can sit on gravel, blocks, or anchors. Medium and large sheds usually need a poured slab, which typically extends about 6 inches beyond the footprint. A foundation must be flat, drained, and not sitting directly on soil, or damp and rot will follow. Check the base size against the external shed dimensions, not just the internal floor area, because wall thickness changes the footprint.
A shed permit depends on local rules, and there is no single national rule. Many jurisdictions exempt sheds under 100 to 120 square feet, some allow up to 200 square feet, and some exempt none at all. Utilities, height, and use can trigger a permit even within a size limit, and setbacks still apply. Always check with the local building department before buying, and treat any permit threshold on a guide page as a local example, not a promise.
Storage grows over time, so buying one size larger than the calculation is usually wise, if the yard and budget allow. Metal shed vs wood shed sizing also differs: metal sheds are often sold by exact footprint, while wood sheds vary by framing and roof overhang, so check external dimensions for both. Shed vs adu is a different question: an adu is a legal living space with insulation, electrical, plumbing, and full code compliance, while a shed is storage or a simple workspace. A well built, proportionate shed can help a property, but no size alone guarantees added value.
The 8 by 10 foot shed and the 10 by 12 foot shed are both very popular. The 8 by 10 suits bikes and tools with room to move, and the 10 by 12 suits a small workspace or hobby area.
Standard sizes include 6 by 8, 8 by 10, 10 by 12, 12 by 16, and 12 by 20 feet. Small sheds are under 100 square feet, medium sheds are 100 to 200 square feet, and large sheds are 200 to 400 square feet.
A riding mower alone needs 10 by 10 or 10 by 12 feet in practice, with a wide enough door to drive it in. Check door width and turning room, not just floor area.
A 12 by 16 foot shed or larger suits a workbench and tools, and a serious workshop needs 16 by 20 feet or larger. Wall height of 8 feet helps with shelving and standing work.
A 10 by 12 to 12 by 20 foot shed suits a desk, chair, shelving, and storage, with room to move. Insulation, power, and light matter as much as floor area for office use.
It depends on local rules. Many areas exempt sheds under 100 to 120 square feet, but some allow up to 200 square feet and some exempt none. Utilities, height, and setbacks can still trigger a permit, so check locally first.
Small sheds can use gravel, blocks, or anchors. Medium and large sheds usually need a poured slab. Any foundation should be flat, drained, and clear of soil contact.
A 36 inch door suits boxes and hand tools. Bikes, mowers, and bulky equipment need a double or wider door, so measure the widest item plus its turning clearance before ordering.
Most sheds have 7 to 8 foot sidewalls. Eight foot walls suit workshop use better, because they allow taller shelving and easier standing work.
Cost varies by size, material, foundation, roof, finishes, and whether it is built by the buyer or hired out. Larger sheds cost more, but no single price fits all sheds, so get local quotes for the size and material you choose.
An adu is a legal living space with insulation, electrical, plumbing, and full code compliance. A shed is storage or a simple workspace, and converting one into living space needs permits and code work.