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Deck Cost Calculator
Use this free deck cost calculator to estimate what a new deck will cost before you call a contractor. Enter the deck size, pick a material tier — pressure-treated wood, cedar, or composite — choose the deck height, and tick the extras you want, such as railing, stairs, lighting, and a permit. The calculator gives a low and high installed cost range, so you can budget honestly and spot a quote that is far above or below the going rate. For board counts and framing quantities, see our deck calculator instead — this page covers cost only.
Extras
How it works
Deck cost starts with area times a per-square-foot rate. The rate depends mainly on the decking material, and the three tiers in this calculator cover the choices most homeowners pick between. Pressure-treated wood is the budget option at $15 to $25 per square foot installed: it is real wood, easy to cut and fasten, and widely available, but it needs sealing every year or two and boards may warp, crack, or rot over time. Cedar sits in the middle at $20 to $35 per square foot: it looks better than treated pine, resists insects and rot naturally, and weathers to a silver grey if left unstained, but it is softer and still needs care. Composite decking is the premium option at $30 to $50 per square foot: boards made from wood fiber and plastic that need no staining, resist rot and insects, and last 25 to 30 years, but cost roughly twice as much up front and get hot in direct sun.
The rate is a range, not a single number, because labor, site access, and local prices vary. A flat backyard with easy truck access and a simple rectangular shape lands near the low end; a sloped yard, a tight side passage, curved edges, or a pattern like diagonal or herringbone boards pushes the price toward the high end. The calculator shows both ends so you can budget for the likely range rather than a single hopeful figure. If a contractor quotes far below the low end, ask what is missing — the quote may exclude railing, footings, or the permit. If a quote is far above the high end, ask what is driving it.
Height is the biggest cost driver after material. A ground-level deck under 3 feet high sits on short posts or concrete blocks and needs no staircase and often no railing, so it uses the base rate as-is. A raised deck 3 to 6 feet high needs taller posts, beams, bracing, and at least one staircase, and this calculator adds about 15 percent. A second-story deck over 6 feet high needs taller posts, deeper footings, structural bracing, and a full staircase with landings, and it adds about 30 percent. Height also triggers railing rules in most places: any deck more than 30 inches above the ground typically needs a guardrail, which is why railing is a separate extra rather than part of the base rate.
The extras are priced as low-to-high ranges and added after the height factor, because they are separate jobs with their own materials. Railing runs $1,500 to $3,000 for a typical deck, depending on length and style — wood balusters are cheapest, metal and cable railing cost more. Stairs run $600 to $1,200 per set, depending on the number of treads and whether they need a landing. A building permit typically costs $200 to $500, and most attached or raised decks need one. Deck lighting runs $400 to $900 for post-cap lights and stair lights, which are cheap to add during construction and expensive to add later. Tick only the extras your project needs; a ground-level deck often needs none of them.
What this estimate does not include is worth knowing before you budget. Demolition and disposal of an old deck, grading or drainage work, and a roof or pergola over the deck are all separate costs. So is furniture, planters, and a grill. The estimate also assumes standard footings in normal soil; rocky ground, a high water table, or a deck built over a slope can add footing costs. Finally, prices move with lumber and labor markets, so treat this as a planning range for comparing quotes, not as a bid — get at least three written quotes from local builders, each itemizing materials, labor, railing, stairs, and the permit, and compare them line by line against this range.
One money-saving tip: keep the shape simple. Every corner, angle, and curve adds cutting time and waste, and a rectangle costs less per square foot than the same area in an L-shape or a multi-level design. Another is to build in the off-season if your climate allows it — contractors are busiest in spring and often price more keenly in late fall. And if you are choosing between cedar and composite, price the maintenance too: a treated or cedar deck needs sealing every one to two years, which over 20 years can close much of the gap with composite.
Worked example
A ground-level deck measures 20 feet long and 15 feet wide, built with pressure-treated wood and no extras.
Step 1: Area — 20 × 15 = 300 square feet.
Step 2: Low cost — 300 × $15 = $4,500.
Step 3: High cost — 300 × $25 = $7,500.
Step 4: Height — ground level, factor 1.00, so no change.
Step 5: Extras — none selected, so nothing added.
The deck costs about $4,500 to $7,500 installed. The same 300 square feet in composite would run $9,000 to $15,000, and adding railing and a permit would add $1,700 to $3,500 to either figure.
FAQ
How much does a deck cost per square foot?
Installed deck cost is typically $15 to $25 per square foot for pressure-treated wood, $20 to $35 per square foot for cedar, and $30 to $50 per square foot for composite decking. The range covers materials and labor, and extras such as railing, stairs, and permits add more.
How much does a 300 square foot deck cost?
A 300 square foot pressure-treated deck at $15 to $25 per square foot costs about $4,500 to $7,500 before extras. The same size in cedar runs about $6,000 to $10,500, and in composite about $9,000 to $15,000, before railing, stairs, and permits.
Is composite decking worth the extra cost?
Composite costs roughly twice as much as pressure-treated wood up front, but it needs no staining or sealing, resists rot and insects, and lasts 25 to 30 years or more. Pressure-treated wood is cheaper to build but needs regular sealing and board replacement, so composite often costs less over the life of the deck.
Do I need a permit to build a deck?
Most areas require a permit for a deck that is attached to the house or more than a couple of feet off the ground, and some require one for any deck over a certain size. Permit fees typically run $200 to $500. Check with your local building department before ordering materials.
What adds the most cost to a deck project?
Height adds the most. A ground-level deck is the cheapest, a raised deck a few feet off the ground adds about 15 percent for posts, beams, and stairs, and a second-story deck adds about 30 percent for taller posts, structural bracing, and a full staircase. Railing is the next biggest extra, especially metal or cable railing.