United Kingdom · Calculator

Decking calculator

Enter the deck size and board size. The calculator works out rows, boards with waste, joists at your chosen centres and an estimate of clips or screws. Add your own unit prices to get a total and cost per m².

Updated 30 Oct 2026 United Kingdom · prices in GBP 10 sources

Decking calculator

Metric · GBP
Deck size
m
m
Boards run along
Boards
Choosing a product fills in its published size and any verified price.
mm
mm
mm
Use the gap your clips or the manufacturer specify.
%
5–10% for simple rectangles; more for angles.
Frame & fixings
mm
Use the maximum from your board’s installation guide. Commercial use often needs closer centres.
Prices (GBP, your quotes) — optional

We do not fill in typical prices: Teosad only uses prices it has verified with a date and source. Enter quotes you have, or choose a product with a verified price.

Rectangular decks only. Split L-shapes into rectangles and add the results. Prices include VAT only if your quotes do.

26boards of 3.6 m to order
12 m²deck area
  • Board rows21
  • Board run (each row)4 m
  • Linear metres of board84 m
  • Boards before waste24
  • Waste allowance (10%)+2
  • Joists at 400 mm centres11 × 3 m
  • Joist linear metres33 m
  • Hidden clips (estimate)≈ 231
Add pricesMissing: Decking boards, Joists, Hidden clips

The run is longer than one board, so rows need joints. Every board end must land on a joist (often a double joist); check your manufacturer’s guide.

If offcuts cannot be reused in other rows, you may need up to 42 boards. Consider a board length that divides the run more evenly.

How this was calculated
  1. rows = ceil((3,000 + 5) ÷ (145 + 5)) = 21
  2. linear metres = 21 × 4 = 84 m
  3. boards = ceil(84 × 1.1 ÷ 3.6) = 26
  4. joists = ceil(4,000 ÷ 400) + 1 = 11

How much does decking cost?

For an installed deck in 2026, expect somewhere between £40 and £220 per m² depending on the material, the frame and the site. Two UK guides we read give the range, and they don’t match because they scope the job differently.

MaterialMyJobQuote, installed per m²BestBuilders, supply and build per m²
Pressure-treated pine£40 to £57softwood £80 to £140
Redwood£67 to £83softwood £80 to £140
Cedar£70 to £87softwood £80 to £140
Hardwood (American)£87 to £105hardwood £140 to £220
Composite£65 to £110£120 to £220

MyJobQuote’s figures are for an average 30 m² job, updated in October 2026. BestBuilders’ 2026 guide covers a standard frame on level ground, adds London at £130 to £230, and prices balustrades at £60 to £150 per metre and steps at £80 to £200 each. Neither says whether VAT is included. A composite supplier, Ultra Decking, puts a fully installed composite deck at £130 to £203 per m² with VAT, labour alone at £60 to £90, a timber subframe at £24.95 and clips and screws at £8.24; it sells composite, so weigh its numbers accordingly.

A worked example: a 4 by 3 m deck is 12 m². At BestBuilders’ prices that is £960 to £1,680 for softwood and £1,440 to £2,640 for composite.

What does a real build cost?

One UK DIYer built a 23.5 m² timber deck in 2024 and itemised it on video:

  • Subframe about £751, the dearest part.
  • Boards about £563.
  • Groundworks about £191 (twelve concrete pads with fence post stilts).
  • Fixings about £272, of which stainless deck screws were about £90.
  • Joist tape about £12 a roll.

He totals about £1,750, or around £75 per m², with VAT but without his own labour. They are his figures, not quotes. He found the same screws about three times the price in a big DIY store and bought online from a specialist instead. He guesses a tradesperson might charge £3,000 to £4,000 for the same deck, which he says is a guess and varies by region.

How much do decking boards cost?

Boards are the smallest part of a decking bill. Wickes sells timber boards from £7 to £25 each: £8 for a 25 by 120 mm board in 2.4 m, £25 for a 27 by 144 mm board in 4.8 m. Cladco puts timber boards alone at about £22 per m², excluding frame and fixings. Composite boards we have checked run £24.32 to £38.99 each:

BoardSizePrice per boardPer metrePer m² of deck
Cladco Signature (hollow)150 mm by 4 m£24.32£6.08£39.23
Envirobuild Explorer (uncapped)145 mm by 4 m£25.99£6.50£43.32
Cladco ProDeck143 mm by 4 m£30.82£7.71£52.06
Cladco Signature Solid150 mm by 4 m£35.26£8.81£56.87
Envirobuild Frontier (capped)142 mm by 4 m£38.99£9.75£66.31

Per metre is the price divided by board length, and per m² divides that by board width plus a 5 mm gap. They are board-only prices that exclude the frame, fixings, delivery and labour. The sample is small, so don’t read it as the market.

How do I use the decking calculator?

Enter the deck length and width, the board size, the gap and a waste allowance. The calculator returns rows, boards with waste, joists at the centres you choose and an estimate of clips or screws. Open the price panel to type in your own prices for boards, joists, fixings, supports and labour. It shows a total only for the lines that have a price, flags the result as partial if a required one is missing, and divides the total by the deck area for a cost per m².

Waste is yours to set. EnviroBuild says to allow 5 to 10 percent for cuts and 15 percent or more for diagonal or herringbone layouts. For joist centres, use your board maker’s figure: Millboard says 400 mm, Composite Prime 300 mm.

Is a deck estimator useful for planning?

It gives you a materials list to price up, and a sense of scale before you ask for quotes. It isn’t a quote and can’t see your site. See composite decking prices for dated board prices, installation costs for labour, and cheaper options if budget is tight.

Questions

Is the decking calculator free?

Yes, and there is nothing to sign up for. It runs in your browser, so what you type stays on your device. The free deck estimator also prints its formulas under the result so you can check the working.

How much decking do I need?

Work out rows by dividing the deck width by board width plus gap, multiply by the run for metres, then divide by board length and add 5 to 10 percent for waste. The board calculator does it and warns you when offcuts can't be reused.

How much does a deck cost per m²?

MyJobQuote's October 2026 figures put installed treated pine at £40 to £57 per m² and installed composite at £65 to £110. BestBuilders gives £80 to £140 for softwood and £120 to £220 for composite, including a standard frame. The two sources differ because they define the job differently.

Does the calculator work out my cost for me?

It multiplies the quantities by the prices you type in. It has no built-in prices, because prices vary by merchant and date, and a missing price is flagged as partial instead of counted as zero.

Is decking cheaper than paving?

We haven't found a named UK source that compares the two like for like, so we won't give a verdict. To compare, ask for an installed price per m² for each, including groundworks, and compare it with the installed decking figures here.

Sources

  1. Timber Decking Boards - Wickes
  2. Composite Decking Cost - MyJobQuote
  3. Composite Decking Board Guide - EnviroBuild
  4. Cost of installing composite decking - Ultra Decking
  5. Timber Decking Cost - MyJobQuote
  6. Decking cost UK - BestBuilders
  7. How much does decking cost - Cladco
  8. HD Deck Pro Fitting Guide and Composite Prime Care & Maintenance Guidelines (Taylor Maxwell, 2022)
  9. Millboard Installation and User Guide (hosted by Cladco)
  10. Installer video: REALITY CHECK! How much does timber decking actually cost in the UK? (Gosforth Handyman)