What waste percentage should I use for hardwood decking?

For standard hardwood decking laid parallel to the house: 12-15% is typical. This accounts for end cuts at each board end, occasional defective boards in hardwood supply and the off-cut when a board is shorter than required at one end of a run. For diagonal decking, use 18-22% due to the larger off-cuts at each corner.

How do I calculate the timber for a wall frame including plates and noggins?

Calculate each element separately: top plates = wall run x 2 (single top plate, double for areas needing it), bottom plate = wall run x 1, studs from the Stud Spacing Calculator, noggins = (studs - 1) x number of noggin rows. Each element has different lengths and may need different grades.

The timber yard quotes in lineal metres -- how do I convert my board count?

Total lineal metres = number of boards x board length. For example, 48 boards at 2.7m = 129.6 lineal metres. Always confirm with the yard whether they quote at a per-board price or a per-lineal-metre price, as some yards price by the piece for standard lengths.

Timber / Lineal Metres Calculator — Free Tradies Calculator

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The frame is drawn up and you need to order the timber. You have an area to board or a known lineal run, board dimensions and a waste allowance. Before calling the timber yard, you need total lineal metres and number of standard lengths.

Timber / Lineal Metres Calculator

Timber

Mode

Area to cover (m²)

Board width (mm)

e.g. 90mm, 140mm, 190mm

Board length (m)

Standard: 2.4m, 3.6m, 4.8m, 5.4m

Gap between boards (mm)

Decking: 6mm · Flooring: 0mm

Waste allowance (%)

Straight run: 10% · Diagonal: 15–20%

Rows = Area ÷ (Board width + Gap in m) Lineal metres = Rows × Run length × (1 + waste%) Waste guide: Straight run: 10% · 45° diagonal: 15–20% · Complex pattern: 20–25%
Always round up to full lengths — short offcuts have limited reuse value.

Reference: Timber Queensland · WoodSolutions Australia

ℹ️ Results are estimates for planning purposes. Verify with current standards and a qualified professional.

1 What this calculator does

Calculates total lineal metres of timber required to cover an area or complete a linear run. From board width, board length, gap between boards and waste percentage, gives total lineal metres needed and number of standard lengths to order.

2 Formula & professional reasoning

Area mode:
  Effective board width = Board width (mm) + Gap (mm)
  Rows needed = Area (m²) / (Effective width in m)
  Lineal metres = Rows needed x (1 + Waste%/100)
Linear run mode:
  Lineal metres = Total run x (1 + Waste%/100)
Boards to order = Ceiling(Lineal metres / Board length)

In area mode, the effective board width includes the gap between boards -- for decking and cladding the gap is a real dimension that affects how many boards are needed. Waste accounts for end cuts, butt joints and the occasional defective board. For hardwood decking with many cut lines, 15% waste is standard. For softwood cladding laid horizontally with few cuts, 10% is typical.

3 Worked examples

⚠️ Illustrative example only — not clinical or professional instruction.

Basic

Hardwood decking over a 45m² deck

Given: Area: 45 m² | Board width: 90mm | Gap: 6mm | Board length: 4.8m | Waste: 12%

Working:

Effective width: (90+6)/1000 = 0.096m | Rows: 45/0.096 = 468.75 lineal metres | With 12% waste: 468.75 x 1.12 = 525 lm | Boards: ceiling(525/4.8) = ceiling(109.4)

Answer: 525 lineal metres | 110 x 4.8m boards to order

💡 At typical hardwood decking price of $8/lm, materials cost is approximately $4,200 plus delivery. Round up to 112 boards for a small buffer.

Standard

Stud wall timber -- linear run

Given: Total stud run: 120 lineal metres | Stud length: 2.7m | Waste: 8%

Working: Lineal metres with waste: 120 x 1.08 = 129.6 lm | Boards: ceiling(129.6/2.7) = ceiling(48)

Answer: 129.6 lineal metres | 48 x 2.7m studs to order

💡 Note this is linear run only -- separate calculations for top plates, bottom plates and noggins are required.

Advanced

Cladding a wall requiring board matching

Working:

Effective width: 0.120m | Rows: 38/0.120 = 316.7 lm | With 15% waste: 316.7 x 1.15 = 364.2 lm | Boards: ceiling(364.2/6.0) = ceiling(60.7)

Answer: 364.2 lineal metres | 61 x 6.0m boards

💡 For lapped weatherboard, use the exposed face (effective width after lap) not the board width. A 150mm board with 30mm lap has a 120mm effective cover width.

4 Sanity check

Typical waste allowances

Straight runs (framing, battens): 8-10% | Decking and cladding: 10-15% | Diagonal or feature laying: 15-20%

Always order whole standard lengths

Boards come in standard lengths (2.7m, 3.6m, 4.2m, 4.8m, 6.0m) | Round up to the next full length

Effective width for lapped cladding

Weatherboard lapped cladding: use exposed face width, not board width

A 150mm board with 30mm overlap has a 120mm effective cover width.

Check timber species and grade availability

Some species only available in shorter lengths -- confirm with the yard before calculating

5 Common errors

Error	Cause	Consequence	Fix
Using board width without including the gap for decking calculations	Dividing area by board width alone	Number of boards significantly underestimated -- run short mid-job	For decking, always use effective width = board width + gap. A 90mm board with a 6mm gap has 96mm effective cover width, not 90mm.
Not applying waste before dividing by board length	Calculating lineal metres net, then dividing by board length	Not enough material when actual waste occurs on cuts and joins	Apply the waste factor to the lineal metre requirement before calculating the number of boards. Waste% increases the lineal metres needed, which then drives the board count.
Forgetting to account for lapped cladding -- using board width instead of exposed face	Not knowing that lapped cladding covers less width than the board	Number of boards significantly underestimated	For lapped weatherboard: exposed face = board width minus the lap dimension. Calculate lineal metres using the exposed face, not the full board width.
Ordering on lineal metres without checking standard lengths available at the yard	Assuming any board length is available	Excessive off-cuts if the only available length is much longer than optimal	Confirm available lengths with the timber yard before calculating board count. If 5.4m boards are available but you calculated on 4.8m, you will have larger off-cuts.