How Much Wood Do I Need?
Quick Answer
There is no single figure: it depends on the project
The method is always the same: measure your area or run in metres, divide by how much one board or sheet covers, then add 10-15% for wastage. Pick your project below for the calculator that does the maths for you.
Find the Right Calculator for Your Project
| Project type | Calculator | What it works out |
|---|---|---|
| Sheet material for an area (plywood, MDF, OSB, chipboard) | Enter the area to cover and the sheet goods calculator returns how many sheets to buy (defaults to a standard 2,440 x 1,220mm sheet with 10% waste). If you have a list of different panel sizes to nest onto those sheets rather than one area total, the plywood cut list calculator packs them and adds its own 5% waste default. | |
| Linear timber (planks, framing, cladding) | Works out how many planks or lengths cover a given area, then prices them once you know the quantity. | |
| An exact cutting list of stock lengths | Enter every individual piece you need to cut from standard-length stock and it works out how many lengths to buy using the actual saw kerf, reporting real waste instead of an estimated percentage. | |
| Decking | Boards, screws and joist spacing for a deck area, board type and gap. | |
| Fencing | Panels, posts, gravel boards and postcrete bags for a boundary run. | |
| Gates | Timber and hardware for a garden or driveway gate. | |
| Tracking waste on a job already underway | Compares what you bought against what you actually used, and benchmarks it against a waste target. |
The General Method (When There Is No Calculator for Your Exact Project)
Every timber quantity question comes down to the same four steps, whether you are panelling a wall or ordering framing for an extension:
- Measure the project. Take the area (length × width) for anything covered edge to edge, such as decking, flooring, cladding or sheet panelling. Take the run length for anything linear, such as skirting, fencing or framing.
- Convert to a single unit, m or m². Multiply mm dimensions by 0.001 per side, so an area in mm² is divided by 1,000,000 to get m². For example, 4,500 × 3,600mm = 4.5 × 3.6m = 16.2 m².
- Work out what one board or sheet covers. For linear stock, that is simply its length. For boards laid edge to edge, it is the board’s face width plus any gap. For sheet goods, it is the full sheet area, a standard UK sheet being 2,440 × 1,220mm ≈ 2.98 m² (the default sheet size in both the sheet goods calculator and the plywood cut list calculator).
- Divide, then add wastage in the right order. For sheet goods, apply the wastage percentage to the area before dividing by sheet coverage, so the total only gets rounded up to a whole sheet once, at the end. For linear stock, round up to a whole number of lengths first, then apply the wastage percentage to that count and round up again. See the worked examples and wastage guidance below for exactly how much to add.
Worked Example: Sheet Material
You need 10 m² of 18mm plywood panelling. A standard UK sheet is 2,440 × 1,220mm:
- 2.44 × 1.22 = 2.98 m² per sheet
- 10 ÷ 2.98 = 3.36 sheets on area alone
- Add a waste allowance for offcuts (the sheet goods calculator defaults to 10%, adjustable 0-50%): 10 × 1.10 = 11 m² needed
- 11 ÷ 2.98 = 3.69, round up to 4 sheets
That is the right method when you just need enough sheets to cover an area. If instead you have a list of different-sized panels to nest onto those sheets, the plywood cut list calculator packs the individual pieces and defaults to a smaller 5% waste allowance (with 5-10% described as typical), since a nested layout of known panel sizes wastes less than an area-only estimate.
Worked Example: Linear Timber
You need 18 linear metres of framing timber, sold in 2.4m lengths:
- 18 ÷ 2.4 = 7.5 lengths on length alone, round up to 8
- Add a waste allowance for cuts and offcuts (the plank calculator defaults to 10%): 8 × 1.10 = 8.8
- Round up to 9 lengths
For an exact cutting list, rather than a single length run, the cut list optimiser packs your individual cut pieces onto stock lengths using the actual saw kerf, so it reports real waste instead of an estimated percentage.
How Much Wastage Should I Add?
The site’s calculators do not all use the same default, because the right allowance depends on how forgiving the cutting layout is:
- Sheet goods, simple area (no cut list): the sheet goods calculator defaults to 10% (adjustable 0-50%).
- Sheet goods, nested panel list: the plywood cut list calculator defaults to 5% (adjustable 0-20%), noting 5-10% as typical, because nesting known panel sizes wastes less than an area-only estimate.
- Standard linear boards and decking: the plank calculator and decking board calculator both default to 10% (adjustable 5-25%).
- Benchmarking waste on a live job: the material waste calculator uses a 15% target as its default comparison point (adjustable 5-40%), for checking how a job is actually running rather than for ordering.
As a rule of thumb: 10% is a sensible default for a simple sheet-goods order by area, 5-10% is enough once you are nesting an exact panel list, 10% covers most linear boards and decking, and complex cut lists with many different lengths, angles or curves (or projects where offcuts genuinely cannot be reused) push toward 15% or more. The order you apply the percentage in also depends on the material: sheet goods apply it to the area before the one final round-up to a whole sheet, while linear stock rounds up to a whole number of lengths first and then applies the percentage to that count, rounding a second time. Follow whichever pattern matches your material, since either way it is cheaper to have one spare length or sheet than to place a second, part-used order.