Lumber Calculator
Calculate board feet, linear metres, piece counts and cost for timber.
Please note: Material estimates for planning only. Always confirm quantities against your drawings, local building codes and supplier specifications before ordering. Structural work requires a qualified engineer.
What the Lumber Calculator does
Timber is sold either by board foot in North America or by linear metre elsewhere. A board foot is 144 cubic inches of nominal timber, and stud counts follow from the run length divided by spacing plus one for the closing member.
Formula
Board feet = Thickness (in) × Width (in) × Length (ft) ÷ 12Studs = ⌊Run length ÷ Spacing⌋ + 1Order quantity = Net quantity × (1 + Waste %)
Inputs explained
| Input | Unit | Required | Notes |
|---|---|---|---|
| What do you need? | one of 2 options | Yes | — |
| Thickness | in | In some modes | Accepts 0.1 or more. Shown What do you need? is Board feet from dimensions. |
| Width | in | In some modes | Accepts 0.1 or more. Shown What do you need? is Board feet from dimensions. |
| Length per piece | number | Yes | Accepts more than 0. |
| Length per piece unit | one of 6 options | Yes | — |
| Number of pieces | number | In some modes | Accepts 1 or more. Shown What do you need? is Board feet from dimensions. |
| Total run length | number | In some modes | Accepts more than 0. Shown What do you need? is Studs or joists for a run. |
| Total run length unit | one of 6 options | In some modes | Shown What do you need? is Studs or joists for a run. |
| Spacing centre to centre | mm | In some modes | Accepts 10 or more. Shown What do you need? is Studs or joists for a run. |
| Waste allowance | % | Yes | — |
| Price per piece | selected currency | Optional | Accepts 0 or more. |
| Currency | one of 10 options | Optional | — |
How to use it
- Choose What do you need? and Length per piece unit.
- Enter Length per piece and Waste allowance.
- Fill in the remaining inputs the form shows for your choice.
- Optionally add Price per piece.
- Select Calculate.
Worked example
Ten 2 × 6 inch pieces, each 3 m long, 10% waste.
- Thickness
- 2 in
- Width
- 6 in
- Length
- 3 m
- Pieces
- 10
3 m = 9.843 ft, so 2 × 6 × 9.843 ÷ 12 = 9.843 board feet each, ×10 = 98.43, +10% = 108.3 board feet.
Frequently asked questions
Why is a 2×4 not actually 2 by 4 inches?
The nominal size is the rough-sawn dimension before drying and planing. The finished piece measures about 1.5 × 3.5 inches, but pricing still uses nominal size.
Why studs plus one?
An 8 m run at 400 mm centres has 20 gaps but 21 studs — you need a member at both ends of the run.