The short answer
To estimate decking cost, measure the area in square metres (length times width), then multiply by a per-metre rate for your chosen material — roughly £100 to £150 per m2 for fitted softwood and £150 to £250 per m2 for hardwood or composite. So a 15 m2 softwood deck estimates at around £1,500 to £2,250. This area-times-rate sum gives a useful starting figure, but it assumes a simple, ground-level deck on flat, accessible ground. Add a margin for raised structure, steps, balustrade, awkward access, sloping ground and design detail, none of which a plain per-metre estimate captures. The result is a budget guide, not a quote — always confirm with itemised estimates for your site.
A quick area-times-rate calculation is the fastest way to get a decking budget in the right ballpark. Knowing which rate to use, and what the simple sum quietly leaves out, keeps the estimate honest.
Estimating decking cost at a glance
- Step 1Measure area: length x width in metres
- Step 2Pick a per-metre rate for your material
- Softwood rateAround £100–£150 per m2 fitted
- Hardwood / composite rateAround £150–£250 per m2 fitted
- Then add forHeight, steps, slope, access, detail
The basic area-times-rate method
The core of any decking estimate is simple arithmetic. Measure the deck area and multiply by a per-metre rate for the material you want:
- Measure the area: for a rectangle, length times width in metres. For an L-shape or stepped layout, split it into rectangles, work out each, and add them together.
- Choose a rate: use a fitted per-metre figure for your material — softwood at the lower end, hardwood and composite higher.
- Multiply: area times rate gives a starting estimate.
- Use a range, not a point: multiply by both the low and high end of the rate to get a band, since real quotes vary.
The worked examples below show the method for a 15 m2 deck. They are indicative for guidance only.
| Material | Per m2 rate | 15 m2 estimate (low–high) |
|---|---|---|
| Softwood | Around £100–£150 | Around £1,500–£2,250 |
| Hardwood | Around £150–£250 | Around £2,250–£3,750 |
| Composite | Around £150–£250 | Around £2,250–£3,750 |
Indicative UK figures for guidance only; a simple estimate for a ground-level deck. Sources: Checkatrade and MyJobQuote 2026 decking cost guides.
What the simple sum leaves out
Area times rate gets you a ballpark, but it quietly assumes the easiest possible deck: a plain rectangle, at ground level, on flat firm ground with good access. Real gardens rarely match that, so the estimate needs adjusting for the things the sum ignores:
- Height: a raised deck needs foundations, posts, steps and a balustrade — a large extra a per-metre surface rate does not include.
- Slope and ground condition: sloping, soft or made-up ground needs more groundworks and a heavier frame than flat, firm ground.
- Access: if materials and waste must be carried through a house or down a narrow passage, labour rises.
- Shape and detail: curves, multiple levels, picture-frame borders and inset lighting add cutting, waste and skilled time.
- Extras and waste: fascia, skirting, steps and a cutting allowance all add to the boards.
For most gardens, treat the area-times-rate figure as the minimum and add a margin for whichever of these apply. A flat, simple, ground-level deck sits near the estimate; a raised deck over a slope with steps and a balustrade can run well above it.
From estimate to reliable budget
A per-metre estimate is a screening tool: it tells you whether a deck is broadly affordable and lets you compare materials before committing. Turning it into a budget you can rely on means refining it with the specifics of your garden. A sensible sequence is:
- Fix the material: decide softwood, hardwood or composite first, since it is the biggest single swing in the estimate.
- Confirm the design: settle ground level versus raised, the shape, and which extras you genuinely want, because each changes the figure.
- Adjust the estimate: take the area-times-rate band and add margins for height, slope, access and detail that apply to your site.
- Get itemised quotes: ask fitters to break out groundworks, subframe, boards, extras and labour, then check their totals against your adjusted estimate.
- Keep a contingency: on sloping or soft ground especially, hold a small reserve for foundations or frame that turn out larger than expected.
Done this way, the simple calculation does its job — getting you to the right ballpark quickly — without being mistaken for a quote. The reliable figure always comes from itemised estimates for your specific deck, with the per-metre sum as the sanity check that they are in the right range.
Frequently asked questions
What per-metre rate should I use to estimate decking?
Use a fitted per-metre figure for your material: roughly £100 to £150 for softwood and £150 to £250 for hardwood or composite. Multiply by your area, using both the low and high end to get a band. Treat the result as a starting estimate for a simple ground-level deck, not a final price.
Should I add extra material for waste when estimating?
Yes. Boards are cut to fit and offcuts cannot always be reused, so order a margin above the bare area. A common rule of thumb is around a tenth extra, more for complex shapes with lots of cutting. A simple area sum that ignores wastage will understate the boards you actually need.
Why is my fitter's quote higher than my area-times-rate estimate?
A plain area-times-rate sum assumes the easiest deck: flat ground, simple rectangle, ground level, good access. A real quote adds for groundworks, the subframe, any raising, steps, balustrade, awkward access and design detail. If those apply to your garden, the quote will sit above the basic estimate, which is normal rather than an overcharge.
Sources & further reading
Figures on this page are typical UK ranges drawn from published sources and depend on your specific garden. They are guidance, not a quotation.