How to Calculate Shed Cost — Step by Step

The short answer

To work out what a shed costs, measure the length and the width, multiply them for the area, add a little extra for offcuts, and price the structure, the foundation and the delivery. For a 10 by 12 ft shed that gives an area of 120.00 square feet and a billable area of 132.00 square feet with 10% extra, a structure cost of $5,280.00 at $40.00 a square foot, plus $300.00 for the foundation and $150.00 for delivery, which is $5,730.00 in total.

The seven numbers that matter

The first number is the size, in feet, measured along the footprint you want for storage. For this shed that is 10 ft long and 12 ft wide. The second number is the extra for offcuts, which is 10% here. The third number is the rate per square foot, which is about $40.00 for a structure installed, including the timber and the labour. The fourth number is the foundation, which is about $300.00. The fifth number is the delivery, which is about $150.00. The sixth number is the budget, which is $4,000 here. The seventh number is the all-in cost per square foot, which is $47.75 here, and it is the number to compare between sheds and between quotes.

The area is the length times the width, which is 10 times 12, which is 120.00 square feet. The billable area is the area times one plus the extra, which is 120 times 1.10, which is 132.00 square feet. The structure cost is the billable area times the rate per square foot, which is 132 times $40.00, which is $5,280.00. The total is the structure plus the foundation plus the delivery, which is $5,280.00 plus $300.00 plus $150.00, which is $5,730.00.

The method

The method is three parts and one addition. One: multiply the length by the width, to get the area. Two: multiply the area by one plus the extra for offcuts, to get the billable area. Three: multiply the billable area by the rate per square foot, to get the structure cost. Four: add the structure, the foundation and the delivery, to get the total. Five: divide the total by the area, to get the all-in cost per square foot.

Step by step

Step 1: find the area. Measure the footprint in feet, with a tape measure, and multiply the length by the width. For this shed that is 10 times 12, which is 120.00 square feet. A shed that follows a slope or a fence is measured in pieces, and the pieces are added up, because the straight-line distance is not the shed.

Step 2: add the extra for offcuts. Multiply the area by one plus the extra, as a decimal. For this shed that is 120 times 1.10, which is 132.00 square feet of billable area. Timber is cut to fit, so about 10% extra is typical, and a shed with windows and a workbench needs more.

Step 3: price the structure. Multiply the billable area by the rate per square foot. For this shed that is 132 times $40.00, which is $5,280.00. The rate is the timber and the labour, so a builder quote and a materials-only price are not the same number.

Step 4: price the foundation and the delivery. The foundation is $300.00 for a slab or skids and the levelling, and the delivery is $150.00 to get the shed to your yard. A shed collected yourself costs $0 for delivery, which brings the total to $5,580.00.

Step 5: add the total. Add the structure cost, the foundation and the delivery, to get the total. For this shed that is $5,280.00 plus $300.00 plus $150.00, which is $5,730.00. The foundation and delivery are $450.00 of $5,730.00, so they are a small part of the job, but they are the part that holds the shed up and gets it to your yard.

Step 6: check the cost per square foot and the budget. Divide the total by the area, to get the number to compare between sheds and between quotes. For this shed that is $5,730.00 divided by 120, which is $47.75 a square foot all-in. And a $4,000 budget minus the $300 foundation and the $150 delivery leaves $3,550, which divided by $40.00 times 1.10 is 80.68 square feet of shed.

The worked example

A homeowner is building a 10 by 12 ft shed, and the structure costs $40.00 a square foot, the extra for offcuts is 10%, the foundation is $300.00, the delivery is $150.00, and the budget is $4,000. The area is 10 times 12, which is 120.00 square feet. The billable area is 120 times 1.10, which is 132.00 square feet. The structure cost is 132 times $40.00, which is $5,280.00. The total is $5,730.00, or $47.75 a square foot. The budget covers 80.68 square feet, which is about 8 by 10 ft, so the shed does not fit the $4,000 budget, and the homeowner either spends more or builds smaller.

A smaller shed, and other round numbers

An 8 by 10 ft shed is 8 times 10, which is 80.00 square feet, so the billable area is 88.00 square feet, the structure is $3,520.00, and the total is $3,970.00, or $49.63 a square foot. Structure at $55.00 a square foot costs $7,260.00, and the total is $7,710.00, or $64.25 a square foot. Structure with 0% extra costs $4,800.00, and the total is $5,250.00, or $43.75 a square foot. With no delivery the total is $5,580.00, or $46.50 a square foot. A 12 by 16 ft shed is 192.00 square feet, the billable area is 211.20 square feet, the structure is $8,448.00, and the total is $8,898.00, or $46.34 a square foot.

Working backwards from a budget

To find how much shed a budget covers, subtract the foundation and the delivery from the budget, then divide what is left by the rate per square foot times one plus the extra. A $4,000 budget minus the $300 foundation and the $150 delivery leaves $3,550. Divide that by $40.00 times 1.10, and it is 80.68 square feet of shed, which is about 8 by 10 ft. An $8,000 budget buys 171.59 square feet, which is about 12 by 14 ft.

Common mistakes

The most common mistake is forgetting the extra for offcuts. A 120 square foot shed is $4,800.00 of structure without the extra, not $5,280.00, so forgetting the extra leaves the shed short by $480.00. The second mistake is forgetting the foundation and the delivery, which together are $450.00. The third is measuring the straight-line distance instead of the shed. The fourth is comparing a materials-only price with a builder quote, which includes the labour. The fifth is forgetting the paint, the shelving, the ramp and the permit, which are not in the model.

The verdict

A 10 by 12 ft shed costs $5,730.00: 120.00 square feet of shed, at $40.00 a square foot with 10% extra for offcuts, plus $300.00 for the foundation and $150.00 for delivery. Measure the length and the width, add the extra, price the structure, and add the foundation and the delivery. Check the numbers on the shed cost calculator, the pergola cost calculator, or the deck cost calculator.