Calculate your shed's square footage from its length and width, then use the result to understand how much usable floor space your planned shed provides.
Whether you're planning a storage shed, garden shed, workshop, equipment shed, or backyard utility building, start with the dimensions that matter.
Calculator results are estimates for planning purposes. Local zoning and permit rules may depend on additional shed characteristics.
Enter the outside dimensions of your planned shed.
Estimated Shed Floor Area
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Shed Planning Guide
A shed size calculator is a planning tool that converts the dimensions of a proposed shed into an estimated floor area. The basic calculation is simple: multiply the shed's length by its width.
That calculation becomes useful when you are deciding whether a particular shed will provide enough room for lawn equipment, gardening tools, bicycles, seasonal storage, workshop equipment, outdoor furniture or other belongings.
Shed dimensions can look relatively small when viewed as two numbers. A 10-foot by 12-foot shed, for example, may initially sound modest. But those dimensions provide 120 square feet of floor area, which can be arranged in many different ways.
Permitrust's shed size calculator gives you a fast starting point for understanding that space before you commit to a design or purchase.
Simple Formula
The floor area of a rectangular shed can be calculated using its length and width.
Shed Area = Length × Width
Example: 12 ft × 10 ft = 120 square feet
Length
The longer horizontal dimension of the shed.
Width
The shorter horizontal dimension of the shed.
Square Feet
The resulting floor area of the rectangular footprint.
Common Dimensions
These examples show how common shed dimensions translate into floor area.
6 × 8 Shed
48 sq ft
8 × 8 Shed
64 sq ft
8 × 10 Shed
80 sq ft
10 × 10 Shed
100 sq ft
10 × 12 Shed
120 sq ft
12 × 12 Shed
144 sq ft
12 × 16 Shed
192 sq ft
16 × 20 Shed
320 sq ft
Choosing a Size
Square footage is important, but it is not the only factor that determines whether a shed will work for your needs.
Make a list of tools, equipment, boxes and other items that need to fit inside.
Measure bulky equipment instead of estimating its footprint.
Leave enough room around stored items for doors, movement and retrieval.
Make sure the proposed shed footprint fits your usable lot area and applicable restrictions.
Plan Around Your Needs
A garden shed may need to accommodate lawn mowers, trimmers, wheelbarrows, gardening tools, fertilizer, hoses and seasonal equipment. Door width and internal access can matter as much as total floor area.
For boxes, decorations, outdoor furniture and household overflow, shelving can significantly increase the usable storage capacity of a shed.
A workshop requires more than storage space. Workbenches, tools, equipment and movement paths can quickly consume available floor area.
If you are storing a riding mower, ATV, trailer equipment or similarly large items, measure the equipment and plan around the entry path before selecting the shed dimensions.
Floor Area Isn't Everything
The square footage calculation describes the shed's floor area, but not every square foot will necessarily function as open storage space.
Shelving, workbenches, cabinets, lawn equipment, doors and walkways all consume space. A larger floor area may therefore be appropriate if you need comfortable access rather than simply enough room to fit your belongings.
Think about how you will use the shed six months or several years from now. Storage needs often grow. Building slightly more space into the original plan can be easier than replacing an undersized shed later.
Floor Area
Total rectangular footprint.
Storage Area
Space occupied by shelves and belongings.
Access Space
Room needed to move and retrieve items.
Permit Planning
Shed size can be relevant when determining whether a project requires a permit or additional review. However, there is no universal shed-size threshold that applies to every property across the United States.
Local requirements may consider floor area, height, location, zoning district, foundation type, use, setbacks and other characteristics.
A small shed may still be subject to zoning restrictions even if a building permit is not required. Conversely, a larger structure may trigger additional review.
Therefore, do not use the square footage result from this calculator as a determination that your shed is permit-free. Check the requirements applicable to your municipality and property.
Before Construction
A shed can fit your storage needs and still be unsuitable for the proposed location.
Check required distance from property lines and other regulated boundaries.
Consider water flow and the existing conditions of the site.
Identify underground or overhead utility concerns before excavation or construction.
Verify zoning, permit and site-specific requirements.
Size Examples
Smaller sheds can work well for gardening tools, bicycles, small lawn equipment and seasonal storage. Organization becomes especially important as floor space is limited.
Medium-sized sheds can provide substantially more flexibility for lawn equipment, household storage, shelving and larger items.
Larger structures may accommodate substantial equipment, workshop layouts and multiple storage zones, but they also deserve closer attention to zoning, permits, setbacks and construction requirements.
Avoid These Mistakes
A cheaper, undersized shed can become expensive if you later need additional storage or replacement space.
Large equipment needs enough room to enter and exit the structure. Interior floor area alone does not solve access problems.
A shed that technically fits everything but leaves no room to walk or retrieve items may be frustrating to use.
Shed size, location and construction details can affect zoning or permit requirements depending on the jurisdiction.
Shed Planning
Choosing the right shed size starts with understanding what you actually need to store. A shed is more than an empty rectangle. Its doors, shelving, wall space, equipment placement and walking paths all affect how useful the building will be.
A shed size calculator is useful because it turns simple dimensions into a number that is easier to compare. Instead of thinking only about whether a shed is 8 feet, 10 feet or 12 feet wide, you can compare the resulting floor areas and decide which configuration provides enough room.
For example, changing a shed from 10 × 10 feet to 10 × 12 feet increases the floor area from 100 square feet to 120 square feet. That additional 20 square feet can make a meaningful difference when you need room for shelving, equipment or a clear walking path.
However, more square footage is not automatically better. The shape of the shed can influence how efficiently the space is used. A long, narrow building may provide the same total area as a more square footprint while creating a different storage layout.
Before selecting a shed size, measure the largest items you plan to store. Include lawn mowers, bicycles, wheelbarrows, outdoor furniture, tools and any equipment that requires a clear path. Then consider how frequently those items will be accessed.
A shed that contains rarely used seasonal boxes can be organized differently from a shed that houses a lawn mower you need every week. Your storage habits should influence the dimensions and internal layout.
You should also consider future needs. Storage requirements tend to increase over time, and a little extra capacity can provide useful flexibility. At the same time, an unnecessarily large shed can create additional planning, cost and regulatory considerations.
The final shed location matters as much as the size. Before construction, check the available space on your property and identify property lines, required setbacks, easements, drainage considerations and other site constraints.
Local shed regulations can also vary significantly. Some jurisdictions may use floor area or structure dimensions as one factor in determining permit requirements, while zoning rules may impose separate limitations on location, height or setbacks.
That means a shed size calculator should be treated as a planning tool rather than a permit determination. Use the calculated floor area to understand your proposed structure, then verify the rules applicable to your property.
Before You Build
Calculating your shed's dimensions is only the first step. Your municipality may have requirements for shed size, setbacks, height, placement, zoning and permits.
Check My Shed Permit RequirementsFrequently Asked Questions
Calculate the floor area of your planned shed, then verify the zoning, setback and permit requirements before construction.
Check Shed Permit Requirements