How much does a deck cost?

A deck's materials cost is a short list of countable parts — joists, boards, posts, footings — multiplied by what your yard charges today. Not a single price per square foot. Build the bill for your deck size below, then price each line.

01 How the math works

Deck cost splits cleanly into two parts: how much of each thing you need, and what each thing costs. The first part is fixed by the deck's size and by code — a 12 ft wide deck at 16 in on-center takes the joists it takes, whatever lumber costs that week. The second part is local and moves constantly.

So the calculator counts the bill of materials from the deck layout, then multiplies each line by the unit price you enter. The counts come from the same math as our deck materials calculator: joist count is the on-center divisions plus the one end joist the bare division always drops, and deck-board count is figured from the board's actual face width plus the gap, not the nominal size on the tag.

We don't print a single price per square foot, because that number is accurate for exactly one deck, somewhere, last year. The honest materials figure is your own bill times your own supplier's prices.

02 Worked example

Take a 12 ft × 16 ft ground-level deck (3.66 m × 4.88 m), joists spanning the 12 ft direction at 16 in (406 mm) on-center, 5/4×6 decking in 16 ft (4.88 m) boards, one beam on posts at 8 ft (2.44 m) on-center.

The bill comes out to 13 joists (each 12 ft / 3.66 m long), 26 rows of decking — 29 boards with a 10% waste factor — and 3 posts on 3 footings. Add the beam and ledger, the railing, the stairs if any, and a box of structural screws and joist hangers.

That bill is the same list in Toronto, Atlanta, or Perth. The dollar total is those counts times what each costs at your yard on the day you order — which is why the calculator takes your prices rather than guessing them. Price the 29 boards, not a rounded "about 25," and the framing line lands where it should.

03 When this guide is wrong

This is a materials bill, not a project quote. Four things it deliberately leaves out or simplifies:

• It counts materials, not labor, delivery, permits, or demolition. On a deck built by a crew, labor is a large and regional line we don't estimate — a materials-only bill is the part that doesn't change with your zip code. If you're hiring out, get the labor quoted separately against this same bill.
• Pricing from the nominal board width under-orders by about 7%. A "6 in" 5/4×6 board is 5-1/2 in (140 mm) wide and lays with a 1/8 in (3.2 mm) gap, so real coverage is 5-5/8 in. Across a 12 ft (144 in) width that's 26 rows, where the nominal 6 in figure gives 24 — two rows, roughly 7% short. Price the actual count.
• The 10% decking waste factor is calibrated for a plain rectangle. That holds for a straight, square deck on simple framing. For small decks, angled corners, picture-frame borders, or diagonal board runs, real waste runs closer to 15–20%, because every rip cut and mitre leaves an offcut too short to reuse. Bump the waste setting before you price, not after you're short. The exception is a long, straight, rectangular deck — there 10% is already generous.
• One footing line doesn't size the concrete per hole. The calculator counts footings; it doesn't price the concrete in each, which depends on hole diameter and how far below the frost line you dig. For that, run the counts through the post-hole concrete calculator or concrete volume calculator.

04 What to do with the result

Take the counts to your supplier as a line-item list and ask for a price on each: joists, deck boards, posts, footing concrete, beam and ledger stock, railing, and a fastener count. Most yards will quote a materials list faster than they'll quote "a 12×16 deck," and the itemized version is the one you can actually check.

Price the decking off the board count the calculator gives, not the nominal rows, and round every line up to whole units — a deck short two boards stops the same way a slab short half a yard does. Then compare the subtotal against any all-in contractor quote: the gap between them is roughly the labor you'd be paying for.

05 Common questions

How much does a 12×16 deck cost in materials?

The materials bill for a 12×16 deck is 13 joists, 29 deck boards (5/4×6, with waste), 3 posts, and 3 footings, plus the beam, ledger, railing, stairs, and fasteners. The dollar figure is that bill times your local prices. We don't give one number because framing-lumber prices move week to week and vary by region, so a national average is stale the day it's published.

Is it cheaper to build the deck yourself?

Building it yourself removes the labor line, not the materials line — the bill of joists, boards, posts, and footings is the same list whether you or a crew buys it. The savings is whatever that crew would have charged to install it, which is regional and not something this page estimates.

Why doesn't this page give a single price per square foot?

Because a per-square-foot figure blends materials and labor into one number and hides what you actually buy. A 12 ft wide deck needs its 13 joists regardless of the rate, and labor swings with your area and the crew. Separating the countable bill from the local prices is the only way the estimate stays checkable.

What's the cheapest decking material?

The board you pick sets most of the bill, so compare them on the same count: pull the board count from the calculator, then price that count in pressure-treated pine, composite, and hardwood at your yard. The counts don't change with the material — only the per-board price does — which makes it a clean side-by-side.