Deck & patio cost overview
A deck budget is more than square footage. The cost is driven by size, height, attachment, material tier, railing, stairs, footings, demolition and how hard the site is to work. This calculator turns those choices into a transparent material take-off plus labour, permit, waste and contingency allowances.
Because prices vary heavily by region, every unit cost is editable, and the result is shown as a low / expected / high range rather than a single false-precise number. Everything runs in your browser — nothing you type is uploaded.
How much does a deck cost?
As a rough planning anchor, a contractor-built deck commonly lands somewhere between a budget pressure-treated build and a premium composite or PVC build with railing and stairs. Material tier and labour are usually the two biggest levers, followed by height, railing length and foundation type.
Rather than quote one number, set your own material, labour and permit rates and read the expected figure with its range. Treat the output as a planning estimate to size a budget and sanity-check quotes — not as a fixed price.
How this calculator works
The tool keeps two engines separate: a quantity engine that calculates how much material your deck needs, and a cost engine that prices it using rates you control. That separation is what keeps the estimate trustworthy when prices change.
Add one or more rectangular sections for L-shaped or multi-level decks. Pick the scope, attachment, material, foundation and height, then tune any rate. The results rail updates live with the cost range, breakdown and take-off.
How to estimate a deck
- Choose units & currencyPick metric or imperial and your currency; every field follows.
- Set scope & materialChoose new, resurface or replace, the attachment, and the decking material tier.
- Add deck sectionsEnter each rectangle's length, width and copies; add sections for L-shaped decks.
- Set foundation & heightPick the foundation type and deck height, plus railed sides and stair runs.
- Tune costs & labourOpen Costs & labour to edit material prices, labour mode, permit and allowances.
- Read the rangeUse the expected total and its low–high range to size a budget and check quotes.
Material take-off formulas
Quantities come from your dimensions and a few standard spacings. Framing, beam, post and footing counts are deliberately simple planning assumptions — not an engineered span design.
The quantity engine uses these formulas; all lengths are converted to a common unit internally.
Decking boards
rows = ⌈across / (boardW + gap)⌉ ; boards = ⌈rows · run · (1+waste) / stock⌉- Boards run along your chosen direction; rows cover the perpendicular side.
- Off-cuts are pooled across the whole project before rounding up.
Joists
joists = ⌊span / spacing⌋ + 1- Joists run perpendicular to the boards at your on-centre spacing.
- Each joist length equals the opposite section dimension.
Beams, posts & footings
posts = beams · (⌊beamLen / postSpacing⌋ + 1) ; footings = posts- Attached decks drop one beam line for the ledger.
- Concrete piers add π r² d of concrete per footing.
Railing & stairs
railing = (perimeter / 4) · sides ; steps = ⌈height / rise⌉- Railing uses the average side so it works for L-shaped decks.
- Steps come from the finished deck height and your stair rise.
The cost model & ranges
Each quantity is multiplied by an editable unit price to build cost buckets: material, labour, demolition and permit. Contingency, overhead and tax are then layered on as percentages.
The range comes from per-bucket uncertainty: material prices are reasonably knowable, while labour and permits swing more by region and access. Low sums the optimistic ends, high the pessimistic ends, and expected sits in between.
The cost engine prices each quantity and layers percentages on top.
Cost buckets
material + labour + demolition + permit- Each bucket is quantity × your editable unit price.
- Waste is applied to cut materials (boards and framing).
Labour
labour = (base + height + stairs + railing) · access · mode- Mode scales labour: DIY 0, hybrid ½, contractor full.
- Access multiplies labour for limited or sloped sites.
Contingency, overhead & tax
total = hard + permit + contingency + overhead + tax- Contingency and overhead build on hard costs; tax excludes the permit.
- Overhead is a contractor mark-up — leave it at 0 for a homeowner budget.
Low / expected / high
low = Σ optimistic ; high = Σ pessimistic- Material ±10%, labour −20%/+25%, demo ±20%, permit ±30%.
- Percentages are recomputed on each end, not spread twice.
Deck vs patio
Over the same footprint, a patio uses a completely different model: excavation, a compacted gravel base, a sand bed, a paver or poured surface and edge restraint — no framing, footings, railing or stairs. The comparison mode prices both and shows which drivers explain the gap.
Cost is only part of the decision. A raised deck suits sloped or uneven ground and gives you storage underneath; a patio is lower-maintenance and often cheaper on flat, accessible sites. The maintenance notes summarise the trade-off.
Worked examples
Two worked take-offs that show how the quantities fall out of your dimensions. Your prices will differ — these illustrate the method.
Two illustrative take-offs. Your costs will differ — these show how the quantities fall out.
Decking boards for a 5 × 4 m deck
Take-off- Given
- Section 5 m × 4 m, boards along the 5 m length
- Board 140 mm wide, 5 mm gap, 3.6 m stock, 10% waste
- Formula
rows = ⌈width / (boardW + gap)⌉ · boards = ⌈rows · runLength · (1+waste) / stock⌉- Steps
- rows = ⌈4 / 0.145⌉ = 28
- run length per row = 5 m → linear = 28 × 5 = 140 m
- boards = ⌈140 × 1.1 / 3.6⌉ = 43
- Result
- ≈ 43 deck boards
Footings for a freestanding deck
Foundation- Given
- Two beam lines, posts spaced ≤ 1.8 m along a 5 m beam
- Concrete piers, 300 mm diameter, 600 mm deep
- Formula
posts = beams · (⌊beamLen / postSpacing⌋ + 1) · concrete = posts · π r² d- Steps
- posts per beam = ⌊5 / 1.8⌋ + 1 = 3
- total posts = 2 × 3 = 6 footings
- concrete = 6 × π × 0.15² × 0.6 ≈ 0.25 m³
- Result
- 6 footings, ≈ 0.25 m³ of concrete
Common mistakes
The most common budgeting errors are forgetting railing and stairs (often a large share of cost), ignoring demolition and disposal on a replacement, leaving out a permit allowance, and trusting a single number instead of a range.
Site access and height are also routinely underestimated — both push labour up well beyond the per-area base rate.
Frequently asked questions
Common questions about estimating the cost of a deck or a patio.
How much does it cost to build a deck?
It depends mostly on size, material tier, height, railing and labour. Enter your dimensions and rates and read the expected total with its low–high range; the tool builds it from a material take-off plus labour, footing, permit and contingency allowances.
What is the cost per square foot of a deck?
The results rail shows cost per area (per ft² or per m²) for the whole project. It is the grand total divided by deck area, so it already includes labour, railing, stairs, footings, permit and contingency — not just decking boards.
How many footings does a deck need?
The tool estimates one footing per support post, from your beam and post spacing. It is a planning figure: the actual number depends on beam sizing, joist span and local code, so treat it as a starting point for a structural design.
Does attached vs freestanding change the cost?
Yes. An attached deck carries one edge on a ledger bolted to the house, so it needs one fewer beam line and fewer posts and footings. A freestanding deck supports every edge on its own posts.
Do I need a permit for a deck?
Often, especially for attached or raised decks and larger footprints — but the rules are local. The calculator flags when a permit is more likely and lets you budget an allowance; it does not state any specific municipality's requirements.
Is composite more expensive than wood?
Composite and PVC cost more upfront than pressure-treated wood but need far less maintenance. Switch the material tier to see the upfront difference, and read the maintenance notes in the comparison panel for the long-term trade-off.
Is a deck or a patio cheaper?
On flat, accessible ground a patio is often cheaper because it skips framing, footings, railing and stairs. On sloped or uneven sites a deck can win. Turn on the comparison to price both over the same footprint.
How accurate is the estimate?
It is a planning estimate, not a quote. Deck costs vary with region, access, soil, code and contractor workload, which is why the tool shows a range and lets you edit every rate. Use it to size a budget and check quotes.
Does it work in metric and imperial?
Both. Switch units at the top and every dimension, quantity and rate converts. Areas show in m² or ft², lengths in m or ft, and footing concrete in m³ or ft³.
Is the calculator private?
Yes. Every calculation runs in your browser. Nothing you enter is uploaded, and your project is saved only in your own browser's local storage.