Pergola cost calculator

Enter the size, post spacing and rafter spacing for the quantities, then type your own prices for the total.

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This pergola cost calculator estimates the total cost of a rectangular pergola using prices you type in yourself. Enter the length, width, post spacing, rafter spacing and overhang, then add your own prices for posts, beams, rafters, other materials, sales tax, labor and permit. The tool counts the posts, beam length and rafters, then adds up a total and a cost per square foot of post-to-post footprint. The site holds no prices, so every result comes from your numbers, and the quantities appear even before you type any price. It runs in your browser, nothing is uploaded, there is no sign-up, and it is free to use.

How to use the Pergola cost calculator

Type “Length (post to post)” and “Width (post to post)”. Each accepts feet, inches, meters or centimeters.
Type “Most distance between posts”, the largest gap you allow along the long side. Set it equal to the length for four corner posts.
Type “Rafter spacing (inches, center to center)”. It starts at 18 in, which sits inside the 18 to 20 in range one kit maker states.
Type “Beam and rafter overhang past the posts”. It starts at 16 in, the figure that same kit maker states.
Under “Beam pieces side by side”, choose 1 piece per beam line or 2 pieces (doubled).
Type “Waste on beams and rafters (%)”. It starts at 0. Add waste if you expect cuts.
Type your own “Price per post”, “Price per foot of beam” and “Price per foot of rafter”. A blank price counts as zero.
Type “Hardware, footings, finish and other materials ($)” as one lump sum, then “Sales tax on materials (%)”.
Type “Labor ($)” and “Permit and fees ($)” as lump sums.
Read the results: posts, rafters, beam and rafter length, footprint, overall roof with the overhang, total cost and total per square foot of footprint.

If an entry is zero, negative, blank or not a number, the tool shows an error instead of a result. Warnings appear for more than four posts, a side over 40 ft, or a rafter spacing under 6 in.

How many posts does a pergola need?

Posts stand along the two long sides. Each long side gets ceil(length ÷ post spacing) + 1 posts, where ceil means rounding up to the next whole number. Setting the post spacing equal to the length gives four corner posts.

How are pergola beam length and rafter count worked out?

Beams run along the length, one line on each side. Each beam line is (length + 2 × overhang) long, multiplied by one or two pieces side by side, plus any waste. Rafters run across the width. The count is floor((length + 2 × overhang) ÷ rafter spacing) + 1, and each rafter is (width + 2 × overhang) long.

For a 16 ft × 12 ft pergola with posts every 16 ft, 18 in rafters and a 16 in overhang, each beam line is 18.67 ft, so the beams total 37.33 ft. There are 13 rafters of 14.67 ft each, or 190.67 ft in all.

How is pergola cost calculated?

The total is posts + beams + rafters + other materials, plus sales tax on those materials, plus labor and permit. The tool also divides the total by the post-to-post footprint in square feet to give cost per sq ft.

Using the 16 × 12 ft example with your own prices of 50 per post, 3 per foot of beam, 2 per foot of rafter, 100 for other materials, 8% tax, 500 labor and 100 permit, the total is 1,456.80, or 7.59 per sq ft. Enter your installation cost under labor if you hire it out.

What pergola dimensions can I use, and why does the tool not list spans?

The page has a table of common sizes, from 10 × 10 ft to 16 × 16 ft, with the footprint and the overall roof size using a 16 in overhang. Sizes vary by maker. A second table summarizes four kit makers, and their post, beam and rafter sizes differ.

The page gives no spans. Post spacing, rafter spacing, overhang and beam plies are your choices. For a pergola span chart, span tables or rafter spacing limits, use your kit instructions, published span tables, and local rules. Results from this calculator are calculated from your inputs only.

Sources (checked 15 October 2026): pergolakitsusa.com · dutchcrafters.com · theluxurypergola.com · sunsetpergolakits.com

Worked examples

Input	Result
16 × 12 ft, posts at most 16 ft apart, rafters every 18 in	4 posts, 13 rafters of 14.67 ft, 37.33 ft of beam
12 × 12 ft, posts at most 12 ft apart, rafters every 18 in	4 posts, 10 rafters of 14.67 ft, 29.33 ft of beam
20 × 12 ft, posts at most 10 ft apart, rafters every 18 in	6 posts, 16 rafters of 14.67 ft, 90.67 ft of beam
4.8 × 3.6 m, posts at most 4.8 m apart, rafters every 18 in	4 posts, 13 rafters of 14.48 ft, 36.83 ft of beam
16 × 12 ft, posts at most 16 ft apart, rafters every 24 in	4 posts, 10 rafters of 14.67 ft, 41.07 ft of beam

Calculated by the tool above; open it with the same values to see each step.

Frequently asked questions

Is this pergola cost calculator free to use?

Yes. It runs in your browser, nothing is uploaded, and there is no sign-up.

Does the calculator know the cost of a pergola?

No. The site holds no prices. The total is calculated from the prices you type, so it is only as accurate as your numbers.

What are common pergola sizes?

The page lists common sizes such as 10 × 10, 12 × 16 and 16 × 16 ft. Sizes vary by maker, so check the posts and beams in your kit.

What pergola span should I use?

The page gives no spans. Check your kit instructions, span tables and local rules before choosing post and rafter spacing.

Why does the tool show an error or a warning?

An error appears for zero or negative sizes, negative prices, blank spacing or non-numeric entries. A warning appears for more than four posts, a side over 40 ft, or a rafter spacing under 6 in.

Can I get quantities without typing prices?

Yes. The posts, beam length and rafters appear without any price. A cost and a cost per square foot appear once you type at least one price.

How much waste should I add to beams and rafters?

Waste starts at 0%. Add waste if you expect cuts. No source gives a figure, so choose a percentage that fits your plan.

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