What size gazebo do I need?

No code or standard sets one. HomeAdvisor's guide prices 8 by 8, 10 by 10, 10 by 12, 12 by 12, 10 by 20 and 14 by 20 ft gazebos. Measure the space across the corners of a hexagon or octagon, not across the flats, because the corners are what has to clear.

What are the dimensions of an octagon gazebo?

With 5 ft sides, an octagon is 12.07 ft across the flats, 13.07 ft across the corners and 120.7 sq ft. With 4 ft sides it is 9.66 ft across the flats and 77.3 sq ft. The calculator works it out for any side.

How do I calculate the area of a hexagon gazebo?

Area = 2.598 × side². A hexagon with 6 ft sides is 93.5 sq ft and 10.39 ft across the flats.

How much does it cost to install a gazebo?

At HomeAdvisor's $75 to $100 per square foot, a 10 by 12 ft gazebo is $9,000 to $12,000. A custom build adds $5,000 to $11,000 over a kit, and a floor is extra, from $4 to $8 per square foot for a concrete slab.

Is a hexagon or octagon gazebo cheaper?

HomeAdvisor gives a hexagon $3,000 to $8,000 and an octagon $3,500 to $8,000, but those ranges do not scale with size. Priced by area, the cheaper gazebo is simply the smaller one: an octagon has 1.86 times the area of a hexagon with the same side length.

Home › Decking › Gazebo Size and Cost Calculator

Gazebo Size and Cost Calculator

Regular polygon geometry; prices from HomeAdvisor's June 2026 gazebo guide

An octagon gazebo with 5 ft sides is 12.07 ft across and covers 120.7 sq ft, more than a 10 by 10 ft square. HomeAdvisor prices a built gazebo at $75 to $100 per square foot, so the shape and side length decide the cost. This calculator works out the floor area and the across-flats size for any shape, then prices it, and shows where the guide's own ranges do not fit together.

The gazebo

Shape

Side length (hexagon or octagon)

Length (square or rectangle)

Width

Floor

Include a permit

For a hexagon or octagon, enter one side. For a square or rectangle, enter length and width.

Specification summary

Generated from on . Reopen that address to reproduce these figures exactly.

Entered

Result

Published ranges for the jobs entered

Gazebo prices

As each row states
Item	Low	High	Unit
Gazebo, typical project	$1,580	$7,952	total
Gazebo, built	$75	$100	per sq ft
8 x 8 ft	$4,800	$6,400	total
10 x 10 ft	$7,500	$10,500	total
10 x 12 ft	$9,000	$12,000	total
12 x 12 ft	$10,800	$14,400	total
10 x 20 ft	$15,000	$20,000	total
14 x 20 ft	$21,000	$28,000	total
Round	$1,500	$8,000	total
Square or rectangle	$2,000	$12,000	total
Hexagon	$3,000	$8,000	total
Octagon	$3,500	$8,000	total
Twelve-sided	$7,000	$10,000	total
Wood	$4,000	$7,000	total
Metal	$3,000	$8,500	total
Vinyl	$2,000	$3,500	total
Brick	$4,000	$7,500	total
Roof	$2	$30	per sq ft
Custom build over a kit	$5,000	$11,000	added
Screen kit	$500	$800	total
Floor, concrete slab	$4	$8	per sq ft
Floor, pavers	$10	$17	per sq ft
Floor, brick	$10	$20	per sq ft
Floor, stamped concrete	$10	$20	per sq ft
Floor, composite	$15	$40	per sq ft
Floor, wood	$10	$50	per sq ft
Permit	$150	$150	up to
Electrical outlet	$180	$500	total

Source: HomeAdvisor, how much does a gazebo cost. Last price check: September 26, 2026.

At the source's $75 to $100 per sq ft, the top of its typical range, $7,952, buys 80 to 106 sq ft: smaller than the 10 x 10 ft gazebo it prices at $7,500 to $10,500 in the same guide.

Worked example

An octagon gazebo with 5 ft sides, no new floor.

Area. 2 × (1 + √2) × 5² = 120.7 sq ft. Across the flats: 5 × (1 + √2) = 12.07 ft.
Built. 120.7 × $75 to $100 = $9,053 to $12,071.
The guide's octagon range. $3,500 to $8,000, which does not scale with size.

The per square foot figure and the shape figure in the same guide do not overlap for this gazebo.

The formula

The area of a regular polygon from one side, then the published rate:

area = n × s² ÷ (4 × tan(180° ÷ n)) across flats = s ÷ tan(180° ÷ n)

n: number of sides: 6 for a hexagon, 8 for an octagon
s: length of one side, ft

For an octagon that is 4.828 × s²; for a hexagon, 2.598 × s². Cost = area × $75 to $100, plus the floor.

Where the numbers come from

The dimensions are geometry and need no source. The prices are HomeAdvisor's, from its gazebo guide updated 20 June 2026 and read on 26 September 2026.

The guide lists the sizes it prices: 8 by 8, 10 by 10, 10 by 12, 12 by 12, 10 by 20 and 14 by 20 ft. It does not say those are standard sizes, and this page does not either.

Hexagon and octagon sizes from one side

Kits and plans for six and eight-sided gazebos are sold by side length or by the width across, and the two are easy to confuse. Across the flats is the distance between two opposite sides; across the corners is longer. A gazebo has to fit the site across the corners.

Floor area and width for common side lengths, calculated
Side	Hexagon area	Hexagon across flats	Octagon area	Octagon across flats
4 ft	41.6 sq ft	6.93 ft	77.3 sq ft	9.66 ft
5 ft	65.0 sq ft	8.66 ft	120.7 sq ft	12.07 ft
6 ft	93.5 sq ft	10.39 ft	173.8 sq ft	14.49 ft

An octagon with 4 ft sides is 9.66 ft across and 77.3 sq ft, a little less than an 8 by 10 rectangle. With 5 ft sides it is 12.07 ft across and 120.7 sq ft, more than a 10 by 10.

The guide's ranges do not fit together

HomeAdvisor's gazebo guide gives three ways to price the same structure, and they disagree.

By area, $75 to $100 per square foot, which is exactly how its size table is built: 10 by 10 ft at $7,500 to $10,500, 12 by 12 ft at $10,800 to $14,400.

By the typical project, $1,580 to $7,952. At the per foot rate that buys 80 to 106 sq ft, less than the 10 by 10 ft the size table starts pricing at $7,500.

By shape, an octagon at $3,500 to $8,000 whatever its size. A 5 ft octagon at the per foot rate is $9,053 to $12,071, above the whole octagon range.

The likeliest reading is that the typical and shape ranges include kits and the per foot rate is for a built structure, and the guide says a custom build adds $5,000 to $11,000 over a kit. It does not state it outright, so the calculator shows both.

Floor, roof and extras

The guide prices a floor separately: a concrete slab at $4 to $8 per square foot, pavers $10 to $17, brick or stamped concrete $10 to $20, composite $15 to $40 and wood $10 to $50. It prices a custom roof at $2 to $30 per square foot, a screen kit at $500 to $800, an electrical outlet at $180 to $500, and says permit fees can reach $150.

For a gazebo on a new slab, the concrete slab calculator gives the concrete for the area above, and the pergola calculator covers the open-roofed version under IRC Appendix AH.

Frequently asked questions

How much does a gazebo cost?: HomeAdvisor's June 2026 guide gives $1,580 to $7,952 for a typical gazebo, $4,766 on average, and $75 to $100 per square foot for a built one. By size it gives $4,800 to $6,400 for 8 by 8 ft, $7,500 to $10,500 for 10 by 10 ft and $10,800 to $14,400 for 12 by 12 ft.
What size gazebo do I need?: No code or standard sets one. HomeAdvisor's guide prices 8 by 8, 10 by 10, 10 by 12, 12 by 12, 10 by 20 and 14 by 20 ft gazebos. Measure the space across the corners of a hexagon or octagon, not across the flats, because the corners are what has to clear.
What are the dimensions of an octagon gazebo?: With 5 ft sides, an octagon is 12.07 ft across the flats, 13.07 ft across the corners and 120.7 sq ft. With 4 ft sides it is 9.66 ft across the flats and 77.3 sq ft. The calculator works it out for any side.
How do I calculate the area of a hexagon gazebo?: Area = 2.598 × side². A hexagon with 6 ft sides is 93.5 sq ft and 10.39 ft across the flats.
How much does it cost to install a gazebo?: At HomeAdvisor's $75 to $100 per square foot, a 10 by 12 ft gazebo is $9,000 to $12,000. A custom build adds $5,000 to $11,000 over a kit, and a floor is extra, from $4 to $8 per square foot for a concrete slab.
Is a hexagon or octagon gazebo cheaper?: HomeAdvisor gives a hexagon $3,000 to $8,000 and an octagon $3,500 to $8,000, but those ranges do not scale with size. Priced by area, the cheaper gazebo is simply the smaller one: an octagon has 1.86 times the area of a hexagon with the same side length.

Check these numbers yourself

How Much Does a Gazebo Cost?HomeAdvisor, updated 2026-06-20, read 2026-09-26.

How every figure here is verified: Sources & Method. Who builds this: Lucas Pradella, and the method is on About. Found something wrong? Tell us and it gets fixed or removed.

Figures on this page last checked against the source documents on 2026-09-26. Codes are amended locally; confirm against the edition your jurisdiction enforces.

Related calculators

The prices are HomeAdvisor's, read on 26 September 2026, and none is this site's. The dimensions are geometry for a regular polygon.