How to Calculate Pergola Cost — Step by Step

The short answer

To work out what a pergola costs, measure the length and the width, multiply them for the area, and price the structure and the footings. For a 12 by 12 ft pergola that gives an area of 144.00 square feet and a structure cost of $6,480.00 at $45.00 a square foot, plus $300.00 for four footings at $75.00 each, which is $6,780.00 in total.

The five numbers that matter

The first number is the size, in feet, measured along the footprint you want shaded. For this pergola that is 12 ft long and 12 ft wide. The second number is the rate per square foot, which is about $45.00 for a structure installed, including the timber or aluminium and the labour. The third number is the footings, which is 4 for a four-post pergola. The fourth number is the cost per footing, which is about $75.00. The fifth number is the budget, which is $8,000 here.

The area is the length times the width, which is 12 times 12, which is 144.00 square feet. The structure cost is the area times the rate per square foot, which is 144 times $45.00, which is $6,480.00. The footings cost is the number of footings times the cost per footing, which is 4 times $75.00, which is $300.00.

The method

The method is two parts and one addition. One: multiply the length by the width, to get the area. Two: multiply the area by the rate per square foot, to get the structure cost. Three: multiply the footings by the cost per footing, to get the footings cost. Four: add the structure and the footings, to get the total.

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 pergola that is 12 times 12, which is 144.00 square feet. A pergola that follows a slope is measured in pieces, and the pieces are added up, because the straight-line distance is not the pergola.

Step 2: price the structure. Multiply the area by the rate per square foot. For this pergola that is 144 times $45.00, which is $6,480.00. The rate is the timber or aluminium and the labour, so a builder quote and a materials-only price are not the same number.

Step 3: count the footings. A four-post pergola needs 4 footings, and a six-post pergola needs 6. For this pergola that is 4 footings, because it has four posts, one at each corner.

Step 4: price the footings. Multiply the footings by the cost per footing. For this pergola that is 4 times $75.00, which is $300.00. The footing cost is the concrete and the digging, so a pergola that needs deeper footings for frost will cost more.

Step 5: add the total. Add the structure cost and the footings cost, to get the total. For this pergola that is $6,480.00 plus $300.00, which is $6,780.00. The footings are $300.00 of $6,780.00, so they are a small part of the job, but they are the part that holds the pergola up.

Step 6: check the cost per square foot and the budget. Divide the total by the area, to get the number to compare between pergolas and between quotes. For this pergola that is $6,780.00 divided by 144, which is $47.08 a square foot all-in. And an $8,000 budget minus the $300 footings leaves $7,700, which divided by $45.00 is 171.11 square feet of pergola.

The worked example

A homeowner is building a 12 by 12 ft pergola, and the structure costs $45.00 a square foot, the footings are 4 at $75.00 each, and the budget is $8,000. The area is 12 times 12, which is 144.00 square feet. The structure cost is 144 times $45.00, which is $6,480.00. The footings cost is 4 times $75.00, which is $300.00. The total is $6,780.00, or $47.08 a square foot. The budget covers 171.11 square feet, which is about 13 by 13 ft, so the pergola fits with room to spare.

A smaller pergola, and other round numbers

A 10 by 10 ft pergola is 10 times 10, which is 100.00 square feet, so the structure is $4,500.00, and the total is $4,800.00, or $48.00 a square foot. Structure at $30.00 a square foot costs $4,320.00, and the total is $4,620.00, or $32.08 a square foot. Structure at $65.00 a square foot costs $9,360.00, and the total is $9,660.00, or $67.08 a square foot. A 16 by 12 ft pergola with 6 footings is 192.00 square feet, the structure is $8,640.00, the footings are $450.00, and the total is $9,090.00, or $47.34 a square foot. With no footings the total is $6,480.00, or $45.00 a square foot. A 20 by 12 ft pergola with 6 footings is 240.00 square feet, the structure is $10,800.00, and the total is $11,250.00, or $46.88 a square foot.

Working backwards from a budget

To find how much pergola a budget covers, subtract the footings from the budget, then divide what is left by the rate per square foot. An $8,000 budget minus the $300 footings leaves $7,700. Divide that by $45.00, and it is 171.11 square feet of pergola, which is about 13 by 13 ft. A $5,000 budget buys 104.44 square feet, which is about 10 by 10 ft.

Common mistakes

The most common mistake is forgetting the footings. A 144 square foot pergola is $6,480.00 of structure, not $6,780.00, so forgetting the footings leaves the pergola short by $300.00. The second mistake is counting four footings for a six-post pergola, which leaves two posts standing on soil. The third is measuring the straight-line distance instead of the pergola. The fourth is comparing a materials-only price with a builder quote, which includes the labour. The fifth is forgetting the stain, the lighting and the permit, which are not in the model.

The verdict

A 12 by 12 ft pergola costs $6,780.00: 144.00 square feet of structure, at $45.00 a square foot, plus $300.00 for four concrete footings. Measure the length and the width, price the structure and the footings, and add them together. Check the numbers on the pergola cost calculator, the deck cost calculator, or the concrete cost calculator.