Cost & value

Deck Cost by Size: 10×10 to 20×20 in 2026

The same $/sq ft doesn't apply to every deck. Here's what common deck sizes actually cost in 2026 — and the fixed costs that make small decks pricier per foot.

8 min read·Updated 2026-07-19·cost

SemiSoftwares

Independent Software Studio · IRC 2021 cross-checked · 2026-Q1 pricing

As a 2026 rule of thumb, a mid-range deck runs about $40–$60 per square foot installed — so a 12×12 (144 sq ft) lands near $6,000–$9,000, a 16×20 (320 sq ft) near $13,000–$19,000, and a 20×20 (400 sq ft) near $16,000–$24,000. But cost doesn't scale in a straight line: small decks cost more per square foot because permits, footings, stairs and mobilization are fixed no matter how small the deck is. Here's the full size-by-size breakdown.

Deck cost by size chart (2026)

These are installed-cost ranges spanning budget pressure-treated to mid/upper composite builds at ground-to-standard height. Your real number depends on material, height, railings and local labor — get it exactly with the deck cost calculator.

Size (ft)	Area	Budget (PT)	Mid (composite)	Premium
10×10	100 sq ft	$3,000–$4,500	$4,500–$6,500	$6,500–$9,000
12×12	144 sq ft	$4,300–$6,500	$6,000–$9,000	$9,000–$12,000
12×16	192 sq ft	$5,800–$8,500	$8,000–$12,000	$12,000–$16,000
16×16	256 sq ft	$7,700–$11,500	$10,500–$16,000	$16,000–$21,000
16×20	320 sq ft	$9,600–$14,000	$13,000–$19,000	$19,000–$26,000
20×20	400 sq ft	$12,000–$18,000	$16,000–$24,000	$24,000–$33,000

A compact backyard deck sized around 10 by 10 feet with a small bistro set — A small 10×10 deck keeps the total low — but its per-square-foot cost is the highest because fixed costs don't shrink. · Photo: Point3D Commercial Imaging / Unsplash

Why small decks cost more per square foot

It surprises people: a 10×10 deck can cost $40–$65 per square foot while a 20×20 drops toward $35–$55. The reason is fixed costs that don't shrink with the deck:

Permits & inspections cost about the same whether the deck is 100 or 400 sq ft.
Footings, posts and the ledger are a baseline every deck needs.
Stairs are a fixed chunk of cost — a small deck still needs a full stair run.
Mobilization (crew showing up, delivery, setup) is the same trip regardless of size.

Spread those fixed costs over 100 sq ft and the per-foot number is high; spread them over 400 sq ft and it falls. That's why, if you're on the fence between two sizes, going a bit bigger often costs surprisingly little per added square foot. Compare per-foot economics with the cost per square foot calculator.

A tape measure and pencil laid on framing lumber while sizing out a deck — Fixed costs — permit, footings, stairs, mobilization — don't scale down, so the smallest decks carry the highest cost per square foot. · Photo: William Warby / Unsplash

What changes the number most

Material. Pressure-treated is cheapest; composite and PVC add $10–$25/sq ft. See cedar vs pressure-treated and PVC vs composite.
Height. A raised or second-story deck adds taller posts, deeper footings, bracing and code railings — often 30–50% over a ground-level deck of the same size.
Railings. Basic vs aluminum/cable can swing thousands on the same footprint.
Stairs & features. Extra stairs, benches, lighting and a pergola each add up.
Region & labor. Labor is 40–60% of the total and varies widely by market.

A large multi-zone backyard deck with separate dining and lounge areas — Go bigger and the per-foot cost drops — but height, railings and features can raise the total faster than square footage does. · Photo: Zac Gudakov / Unsplash

How to use these numbers

Treat the chart as a sanity-check range, not a quote — then get three itemized bids (see how to read a deck quote).
Pick the size that fits your yard and use, not just a price — an under-sized deck you can't furnish is a false economy.
Remember the per-foot curve: sizing up one increment is usually cheaper per foot than it looks.

The joist and beam framing of a deck under construction, sized out on footings — A bigger deck isn't just more boards — it's more framing, more footings and sometimes larger members underneath. · Photo: Troy Allen / Unsplash

Open the calculator

Price your exact size and material →

Estimate full deck project cost: materials, labor, permits, and per-square-foot pricing for any size and material.

Whatever the size, the framing must meet IRC joist, beam and footing spans — a bigger deck isn't just more boards, it's more (and sometimes larger) structure underneath.

Frequently asked questions

How much does a 12×16 deck cost in 2026?

A 12×16 deck (192 sq ft) typically costs about $5,800–$8,500 in pressure-treated, $8,000–$12,000 in composite, and $12,000–$16,000 for premium builds installed — depending on height, railings and local labor.

How much does a 20×20 deck cost?

A 20×20 deck (400 sq ft) usually runs about $12,000–$18,000 in pressure-treated, $16,000–$24,000 in composite, and up to $24,000–$33,000 premium. Per square foot it's often cheaper than a small deck because fixed costs spread over more area.

Why do small decks cost more per square foot?

Because fixed costs — permits, footings, stairs, and the crew's mobilization — stay roughly the same no matter the size. Spread over a small deck they push the per-square-foot price up; spread over a large deck they fall.

Is it cheaper to build a bigger deck?

Not in total, but often cheaper per square foot. Because fixed costs don't scale down, sizing up one increment usually adds less per added square foot than the base rate — so a slightly larger deck can be surprisingly good value.

What's the average cost per square foot for a deck?

About $30–$60 per square foot installed in 2026, with small decks toward the high end and large decks toward the low end. Material, height and railings move the number more than size alone.