How the Board Foot and Timber Cost Calculator Works
Timber is sold by volume or by length. In the US, hardwood is priced by the board foot; in the UK, sawn hardwood is usually priced by the cubic metre and softwood and planed timber by the linear metre. The calculator works out all of them for each board, adds your waste allowance and prices the lot.
A board foot is a piece one inch thick, twelve inches wide and one foot long: 144 cubic inches. It is a measure of volume, so a 2 in × 6 in board 1 ft long is also one board foot. A cubic metre is 1 m × 1 m × 1 m, which is about 423.8 board feet.
The Formulas
1. Board feet
bd ft = T (in) × W (in) × L (ft) ÷ 12
bd ft = T (in) × W (in) × L (in) ÷ 144
Rough-sawn hardwood uses quarter sizes: 4/4 = 1 in, 5/4 = 1.25 in, 8/4 = 2 in.
2. Cubic metres
m³ = T (mm) × W (mm) × L (mm) ÷ 1,000,000,000
1 bd ft = 0.002359737 m³
1 m³ = 423.776 bd ft = 35.315 ft³
One cubic foot is 12 board feet.
3. Linear metres
linear m = quantity × length (m)
price per m³ = price per m ÷ (T × W in m²)
A linear price only makes sense for one section size, so give each section its own price.
4. Waste and cost
to buy = net × (1 + waste % ÷ 100)
cost = to buy × price
weight = m³ × density (kg/m³)
Priced per piece, the waste rounds up to whole pieces.
Worked Examples
UK: four oak boards, 27 × 200 mm, 2.4 m long, priced per cubic metre
- Each board: 27 × 200 × 2400 = 12,960,000 mm³ = 0.01296 m³. Four boards: 0.05184 m³.
- In board feet: 0.05184 × 423.776 = 21.97 bd ft. In length: 4 × 2.4 = 9.6 linear metres.
- With 15 % waste: 0.05184 × 1.15 = 0.0596 m³ to buy.
- At a round example price of £1,000 per m³ (use your merchant's figure): 0.0596 × 1,000 = £59.62. The same price is £2.36 per board foot, or £5.40 per metre for this 27 × 200 section.
- At a typical 720 kg/m³ for dried oak, the 0.0596 m³ weighs about 43 kg: worth knowing before you load the car.
US: three 4/4 boards, 6 in wide, 8 ft long, priced per board foot
- Each board: 1 × 6 × 8 ÷ 12 = 4 bd ft. Three boards: 12 bd ft.
- With 20 % waste: 12 × 1.2 = 14.4 bd ft. At an example $5 per board foot: $72.
Practical Tips
- Nominal or actual? Rough-sawn hardwood is priced on its nominal sawn thickness, and planed (PAR) timber is often sold by its nominal size even though it measures a few millimetres less. Enter the size your merchant prices by, then plan your parts from the finished size.
- Plan cuts first. Work out how your parts come out of standard lengths with the linear cut list optimizer, then enter the boards you will actually buy here. Sheet goods such as plywood and MDF are better planned with the sheet cut optimizer.
- Allow for planing. Rough boards lose a few mm in thickness and width when you flatten and square them. Buy thick enough to finish at your target size.
- Moisture. Kiln-dried timber for indoor furniture should be acclimatised in the workshop before you cut it. Green or air-dried timber is heavier and still moving.
- Pouring a river table? Pair this with the epoxy resin calculator for the resin, and the CNC router feeds and speeds calculator for flattening the slab. For metal stock weights rather than timber, use the metal weight calculator.
Frequently Asked Questions
Multiply thickness in inches by width in inches by length in feet, then divide by 12. A board 1 inch thick, 6 inches wide and 8 feet long is 1 × 6 × 8 ÷ 12 = 4 board feet. If the length is in inches, divide by 144 instead.
About 423.8. One board foot is 144 cubic inches, which is 0.002359737 cubic metres, so one cubic metre is 1 ÷ 0.002359737 = 423.776 board feet. A price of £1,000 per cubic metre is therefore about £2.36 per board foot.
It is the rough-sawn thickness in quarters of an inch: 4/4 is 1 inch, 5/4 is 1¼ inches, 6/4 is 1½ inches and 8/4 is 2 inches. Board feet are worked out on that nominal thickness, even though the board will be thinner after planing.
It depends on the grade and how well your parts fit the boards. Woodworkers often allow 15 % or more for rough-sawn hardwood, more for lower grades with knots and splits, and less for planed stock cut to lengths you have already planned. Plan your cuts first and adjust the allowance to what you see in the boards.
Divide the price per metre by the cross-section area in square metres. A 27 × 200 mm board has a section of 0.027 × 0.2 = 0.0054 m², so £5.40 per metre is £5.40 ÷ 0.0054 = £1,000 per cubic metre. The price converter on this page does this for your first board's section.
Prices in the examples are round numbers for illustration, not market prices. Densities are typical values for dried timber and vary between boards. Check how your merchant measures and prices before you order.