What is a hoppus foot and why is it still used?

The hoppus foot is a traditional English unit for round timber, calculated from the quarter-girth: volume = (girth ÷ 4)² × length, with girth in inches and length in feet, divided by 144. One hoppus foot is about 1.273 true cubic feet, and it remains the customary measure for hardwood logs in the UK round-timber trade — this calculator converts hoppus feet alongside m³ and cubic feet.

How do I convert a price per linear metre into a price per m³?

Divide the price per linear metre by the cross-sectional area in square metres (thickness in m × width in m). For example, a 38 × 89 mm CLS stud priced at £2 per linear metre works out to roughly £592 per m³. This calculator does that conversion automatically so you can compare quotes given in either basis.

What is the difference between CLS and carcassing timber?

CLS is regularised, eased-edge softwood cut to sizes such as 38 × 63 mm and 38 × 89 mm, mainly used for internal stud partition walls. Carcassing is structurally graded softwood (typically C16 or C24) in sizes like 47 × 100, 47 × 150 and 47 × 225 mm, used for joists, rafters and other load-bearing roof and floor timbers.

Is there a decking calculator built into this tool?

Yes — select the decking board 145 × 28 mm preset in sawn mode, enter your deck dimensions as a length and quantity of boards (or work out the board count yourself using coverage width = board width + gap, then deck width ÷ coverage width), and the calculator returns total volume, waste-adjusted volume and cost. For a worked example: a 3.6 m wide deck with a 5 mm gap between 145 mm boards needs 24 boards to cover the width, plus joists at 400 mm centres underneath.

How many decking boards do I need for my deck?

Add the board width to your expansion gap (typically 5 mm) to get the effective coverage per board, then divide the total deck width by that figure and round up. For example, 145 mm boards with a 5 mm gap cover 150 mm each, so a 3.6 m wide deck needs 3,600 ÷ 150 = 24 boards running the length of the deck. Add roughly 5–10% extra for cutting waste and end trims.

What joist spacing should I use under a deck, and how do I calculate joist count?

Residential decking is normally built on joists at 400 mm centres (some designs use 450 mm — check span tables or manufacturer guidance for your joist size and decking board thickness). To calculate the number of joists, divide the deck width by the centre spacing and add one: for a 3.6 m wide deck at 400 mm centres, that is (3,600 ÷ 400) + 1 = 10 joists.

Does this tool work as a general timber conversion calculator?

Yes. Enter a volume, cut list or log dimension and the results panel shows the equivalent figures in m³, cubic feet, board feet and hoppus feet simultaneously, so you can use it purely as a conversion calculator between UK, US/Canadian and traditional hardwood-trade units without needing a price at all.

How much does a cubic metre of wood cost in the UK?

It varies significantly by species, grade and section size. As a rough 2026 guide, C16/C24 structural softwood carcassing typically costs £320–£480 per m³, with smaller CLS studwork sections often priced higher per m³ than larger carcassing sections. Hardwood such as oak is priced on a different scale entirely, usually per hoppus foot rather than per m³, and can be several times the cost of construction softwood.

Can I use this as a stud wall or floor joist calculator?

Yes — add each section in your stud wall or floor plan as a separate row (for example CLS 38 × 89 mm studs and 47 × 150 mm joists), enter lengths and quantities, apply a waste allowance, and the calculator totals the volume and cost across the whole cut list, as shown in the worked stud-wall example above.

Why doesn't the UK use board feet like the US and Canada?

UK timber has been sold on the metric system since the 1970s, with sawn softwood priced and specified in cubic metres and merchant sections given in millimetres. Board feet remain the standard unit in the US and Canadian lumber trade but are essentially unused at UK retail or trade counters — this calculator includes the board-foot conversion mainly for comparison against North American price lists or specifications.

Timber Calculator – m³ Volume, Cut List & Cost (2026)

Timber Calculator: Work Out m³ Volume, Cut Lists and Cost

In the UK, sawn softwood is bought and sold by the cubic metre (m³), worked out as thickness (mm) × width (mm) × length (m) ÷ 1,000,000 for each piece, then added up across a cut list. Board feet — the unit you will see quoted on American and Canadian lumber calculators — barely features at retail here; if you have landed on this page looking for a "board foot calculator", the number is included in the results, but nobody at a UK builders' merchant will ask for it.

Retail counters more often quote a price per linear metre for a given section (say, £3.40 per linear metre of 47 × 100 mm carcassing) rather than a price per cubic metre, so this calculator converts freely between the two — enter whichever basis your quote is in and it will work out the other automatically.

Round hardwood logs are a different story. Alongside the modern Huber (mid-diameter) rule, the quarter-girth "hoppus" measure survives as the customary way to cube standing and felled hardwood in the UK timber trade, a legacy of 18th-century forestry mathematics that still turns up in woodland valuations and hardwood log price lists today. Use sawn mode for a CLS, carcassing or decking cut list, or switch to log mode to cube round timber under either rule.

Whichever mode you use, the results panel shows the total volume with your waste allowance applied, the m³/ft³/board-foot/hoppus-foot conversions side by side, and an estimated cost if you enter a price — so you can move between a merchant's per-m³ quote, a per-linear-metre quote, and a rough per-piece cost without reaching for a calculator app or a conversion table.

Step-by-step: pricing a stud wall or floor joist cut list

The most common job for this calculator is pricing a cut list for a stud partition, a floor, or a small roof — a handful of different sections, each with its own length and quantity, that need turning into a total volume and a total cost.

Choose "Sawn timber / cut list" mode.
Add a row for each section you need — pick a preset such as CLS 38 × 63 mm, CLS 38 × 89 mm, or Carcassing 47 × 100/150/225 mm, or enter a custom thickness and width.
Enter the length for each row (in mm or as a standard stock length such as 2.4 m, 3.0 m, 3.6m or 4.8 m) and the number of pieces required.
Set a waste/offcut allowance — 10% is a sensible default for straightforward stud and joist work, rising to 15–20% if the cut list involves a lot of trimming or notching.
Enter a price either per m³ or per linear metre, depending on how your merchant has quoted — the calculator converts between the two automatically so you can sanity-check one against the other.
Read off the total volume including waste, the board-foot/hoppus-foot/ft³ conversions, and the estimated total cost, then download the CSV or print it to keep alongside your quote.

Worked example: a stud wall cut list in £/m³ and £/linear metre

Say you are building an internal stud partition and a small run of floor joists. Your cut list is:

12 no. CLS 38 × 89 mm studs at 2.4 m long
6 no. carcassing 47 × 150 mm joists at 3.6 m long
10% waste allowance on both

Worked example continued — the numbers

CLS studs: cross-section is 38 mm × 89 mm = 3,382 mm². Volume per piece = 0.038 m × 0.089 m × 2.4 m = 0.008117 m³. For 12 pieces that is 0.0974 m³ before waste, or 0.1071 m³ with 10% waste added.

Carcassing joists: cross-section is 47 mm × 150 mm = 7,050 mm². Volume per piece = 0.047 m × 0.150 m × 3.6 m = 0.02538 m³. For 6 pieces that is 0.1523 m³ before waste, or 0.1675 m³ with 10% waste added.

Combined total with waste: 0.1071 + 0.1675 = 0.2746 m³.

At a typical merchant price of £380 per m³ for C24 carcassing softwood, that cut list would cost roughly 0.2746 × £380 ≈ £104.

Now cross-check that against a linear-metre quote. If the CLS is quoted at £1.85 per linear metre and the carcassing at £3.10 per linear metre: 12 studs × 2.4 m × £1.85 = £53.28, plus 6 joists × 3.6 m × £3.10 = £66.96, giving £120.24 before waste, or roughly £132 with 10% waste on the linear-metre spend as well.

The gap between the two totals (£104 vs £132) is exactly the kind of thing worth catching before you order — it usually means one quote is priced at a merchant's standard trade rate per m³ while the other linear-metre price includes a retail mark-up, or vice versa. Converting a linear-metre price to £/m³ makes the comparison fair: £1.85 per linear metre for 38 × 89 mm CLS works out to £1.85 ÷ (0.038 × 0.089) ≈ £548 per m³ — noticeably higher than the £380/m³ carcassing rate, which is normal since small-section CLS studwork usually carries a higher per-m³ price than larger carcassing sections.

Worked example: hoppus feet for a round hardwood log

The hoppus (quarter-girth) method is still the customary way hardwood logs are measured and valued in the UK and Ireland, particularly for oak, ash and other broadleaf timber sold standing or at the roadside. The formula is: hoppus feet = (quarter-girth in inches)² × length in feet ÷ 144, where the quarter-girth is simply the girth (the measured circumference) divided by four.

Worked example: an oak log measures 60 inches in girth (roughly 480 mm diameter) and is 12 feet long. Quarter-girth = 60 ÷ 4 = 15 inches. Hoppus feet = 15² × 12 ÷ 144 = 225 × 12 ÷ 144 = 18.75 hoppus feet.

Because one hoppus foot is about 1.273 true cubic feet (it deliberately over-estimates volume slightly, to account for the timber lost squaring a round log into a rectangular baulk), that same log is roughly 18.75 × 1.273 ≈ 23.9 true cubic feet, or about 0.677 m³ true volume.

In practice, buyers and foresters use hoppus feet directly for pricing rather than converting it — a merchant or timber merchant quoting "£45 per hoppus foot for standing oak" is pricing against the hoppus figure, not the true cubic volume, so multiplying straight through (18.75 × £45 ≈ £844) gives the trade value without any extra conversion. Use the hoppus rule in this calculator when you are dealing with round hardwood in the traditional way; use the Huber (mid-diameter) rule instead when a supplier has priced a log on true, modern cubic measure, which is increasingly common for softwood roundwood destined for sawmilling rather than the traditional hardwood log trade.

Worked example: decking boards and joists for a garden deck

Decking is one of the most common searches that brings people to a timber calculator, and the sums are slightly different from a stud-wall cut list because boards run in one direction with a fixed gap between them, and need a joist frame underneath at a standard spacing.

Say you are decking an area 4.0 m long by 3.6 m wide, running boards along the 4.0 m length, using the standard 145 × 28 mm decking board preset with a 5 mm expansion gap between boards.

Effective board coverage width = board width + gap = 145 mm + 5 mm = 150 mm. Number of boards needed = deck width ÷ effective coverage = 3,600 mm ÷ 150 mm = 24 boards.

Each board needs to span the 4.0 m length, so at a standard 3.6 m stock length you would need to join boards or, more practically, order the 4.8 m stock length and trim 0.8 m of offcut per board (which becomes useful waste for noggins and trims). Total decking board volume: 24 boards × 0.028 m × 0.145 m × 4.0 m = 24 × 0.01624 m³ = 0.3898 m³, or roughly 0.43 m³ with 10% waste for cutting and trimming.

For the joists underneath, standard practice is 400 mm centres for residential decking (some designs use 450 mm, but 400 mm is the safer, more common default). Number of joists = (deck width ÷ 400 mm) + 1 = (3,600 ÷ 400) + 1 = 9 + 1 = 10 joists, each 4.0 m long (matching the span the boards need supporting), typically in 47 × 100 mm or 47 × 150 mm carcassing depending on the span and ground support spacing.

Add these two totals in the calculator as two rows — decking boards and joists — with their own prices, and the results panel gives you a single combined cost and volume for the whole deck structure.

Conversion table: m³, board feet, hoppus feet, cubic feet and £/linear metre

1 m³ = 35.315 cubic feet (ft³)
1 m³ = 423.776 board feet (1 board foot = 1 in × 12 in × 1 ft = 1/12 ft³)
1 m³ ≈ 27.737 hoppus feet (since 1 hoppus foot ≈ 1.273 true ft³, and 35.315 ÷ 1.273 ≈ 27.74)
1 hoppus foot ≈ 1.273 cubic feet ≈ 0.0361 m³
1 board foot ≈ 0.002360 m³ ≈ 0.0833 ft³
£ per m³ → £ per linear metre: £/m³ × (thickness in m × width in m) = £/linear metre, for a given section
£ per linear metre → £ per m³: £/linear metre ÷ (thickness in m × width in m) = £/m³, for a given section
Example: £380/m³ for 47 × 150 mm carcassing = £380 × (0.047 × 0.150) = £2.68 per linear metre

How timber is actually priced in the UK

Trade and merchant pricing almost always starts from a £ per m³ figure for a given grade and species, then gets converted to a £ per linear metre shelf price for the sizes a branch stocks. As a rough 2026 guide, C16/C24 structural carcassing softwood typically runs from around £320 to £480 per m³ depending on section size, grade and local supply, with smaller sections and CLS studwork often priced higher per m³ than large carcassing because of the extra processing per piece. Pressure-treated decking boards commonly work out to somewhere between £2.50 and £5.50 per linear metre for standard 145 × 28 mm sections, depending on the treatment class and whether it is a smooth, reeded or grooved profile. Hardwood — oak in particular — is priced on a completely different scale, often quoted per hoppus foot or per true m³ at figures several times higher than construction softwood, reflecting slower growth, lower yield per log, and finishing quality.

Prices vary by region, by branch, and with global softwood supply (much of the UK's carcassing timber is imported, principally from Scandinavia, the Baltic states and Russia-adjacent supply chains that shifted after 2022), so treat any figure here as a planning estimate rather than a quote, and always get a current price from your merchant before ordering in volume.

Grading, species and buying tips

Structural softwood sold in the UK is graded to BS EN 338, with C16 and C24 the two grades you will meet at almost every builders' merchant. C16 is the standard grade for general carcassing — floor joists, rafters, studwork — while C24 is a stronger grade used where spans are longer or loads are higher; a timber engineer's span table or building control will specify which grade a particular job needs. The grade stamp on the timber (along with the CE or UKCA mark and the supplying sawmill's licence number) is your evidence that a piece has actually been strength-graded rather than just visually sorted.

Most structural and carcassing softwood sold in Britain is imported whitewood or redwood (spruce or pine) from Scandinavia and the Baltic, though home-grown Sitka spruce and Douglas fir from UK and Irish forestry also supply a meaningful share of the market. For decking, modified and pressure-treated softwood dominates the budget end, while hardwood decking (such as balau or oak) and thermally modified softwood sit at the premium end. For furniture, joinery and high-value hardwood work, home-grown oak, ash and sweet chestnut remain the traditional choices, still measured and often still priced by the hoppus foot when bought as a log rather than sawn stock.

TRADA (the Timber Research and Development Association) is the standard UK reference body for span tables, grading guidance and timber specification, and is worth knowing about if you want to go beyond a rough calculator estimate into a proper structural design. When buying at a merchant's counter, it is worth asking specifically whether a quoted price is per m³ or per linear metre, whether it includes delivery, and whether the grade stamped on the timber matches what your design (or building control) actually requires — carcassing sold without a visible strength grade is not something building control will sign off for structural use.

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Timber Calculator: Volume, Cut List & Cost