Sizes, waste and price
Type sizes like 2, 3 1/2 or 8/4 (hardwood quarters) and lengths like 8 or 8'6". Add a board for each size you buy — a new board starts as a copy of the last one. Everything is saved on this device.
About the board foot calculator
This free board foot calculator works out how much lumber you have or need. A board foot is a piece of wood 1 inch thick, 12 inches wide and 1 foot long — 144 cubic inches. Hardwood and a lot of lumber is priced by the board foot.
Add a line for each size of board: its thickness, width, length and how many. You get the board feet of each line and the total, the cubic feet and m³, the linear feet, and the cost from the price per board foot.
Features
- A list of boards — any number of sizes, each with its own count
- Board feet per line and in total — plus cubic feet, m³ and linear feet
- Nominal or actual sizes — count a 2 × 4 the way the yard does, and see the planed wood too
- Hardwood quarters — type 4/4, 5/4 or 8/4 for the thickness
- Waste — add 10–30% for defects and cuts
- Cost — price per board foot (per m³ in metric)
- Metric — mm and metres, with m³ first and board feet next to it
- Saved on this device — the list is still there at the lumber yard
The board foot formula
Board feet = thickness (in) × width (in) × length (ft) ÷ 12
Or with all sizes in inches: thickness × width × length ÷ 144. Then multiply by the number of boards.
- 1 board foot = 144 cubic inches = 1/12 cubic foot = 0.00236 m³
- 1 cubic foot = 12 board feet
- 1 m³ = 423.8 board feet
Board feet of common lumber
Nominal is the size the board is sold as. Actual is the planed size of softwood lumber: a 2 × 4 is really 1½ × 3½ in.
| Lumber | Board feet (nominal) | Board feet (actual wood) |
|---|---|---|
| 1 × 4 × 8 ft | 2.67 | 1.75 |
| 1 × 6 × 8 ft | 4.00 | 2.75 |
| 1 × 12 × 8 ft | 8.00 | 5.63 |
| 2 × 4 × 8 ft | 5.33 | 3.50 |
| 2 × 4 × 10 ft | 6.67 | 4.38 |
| 2 × 6 × 8 ft | 8.00 | 5.50 |
| 2 × 6 × 12 ft | 12.00 | 8.25 |
| 2 × 8 × 10 ft | 13.33 | 9.06 |
| 2 × 10 × 12 ft | 20.00 | 13.88 |
| 2 × 12 × 16 ft | 32.00 | 22.50 |
| 4 × 4 × 8 ft | 10.67 | 8.17 |
| 6 × 6 × 10 ft | 30.00 | 25.21 |
The tool finds the actual size with the usual planed sizes: under 2 in take off ¼ in, from 2 to 7 in take off ½ in, from 8 in take off ¾ in.
Hardwood thickness in quarters
Rough hardwood is sold in quarters of an inch. You can type these straight into the thickness box:
| Quarters | Thickness |
|---|---|
| 4/4 | 1 in |
| 5/4 | 1¼ in |
| 6/4 | 1½ in |
| 8/4 | 2 in |
| 12/4 | 3 in |
| 16/4 | 4 in |
Worked examples
- Framing lumber: 10 boards of 2 × 4 × 8 ft = 2 × 4 × 8 ÷ 12 × 10 = 53.33 board feet (35.00 board feet of actual wood).
- Hardwood: 3 boards of 8/4 × 8 in × 10 ft = 2 × 8 × 10 ÷ 12 × 3 = 40 board feet. At $12.00 a board foot that is $480.00. With 20% extra for defects and cuts: 48 board feet, $576.00.
- Metric: 10 boards of 45 × 95 mm × 2.4 m = 0.045 × 0.095 × 2.4 × 10 = 0.103 m³ = 43.5 board feet.
Frequently asked questions
What is a board foot?
A volume of wood: 1 in thick, 12 in wide and 1 ft long, which is 144 cubic inches. A board 2 in thick, 6 in wide and 1 ft long is also 1 board foot.
How do I calculate board feet?
Multiply thickness (in) × width (in) × length (ft) and divide by 12. A 2 × 6 that is 10 ft long is 2 × 6 × 10 ÷ 12 = 10 board feet.
How many board feet are in a 2 × 4 × 8?
5.33 board feet by its nominal size, which is how lumber yards count it. The wood itself (1½ × 3½ in) is 3.5 board feet.
Should I use nominal or actual sizes?
Use nominal sizes to match a price list for softwood lumber. Use actual sizes when you measure rough or odd boards yourself, or to know how much wood you really have.
How many board feet are in a cubic meter?
423.8 board feet. One board foot is 0.00236 m³, and one cubic foot is 12 board feet.
How much extra lumber should I buy?
Many woodworkers add 15–30% for hardwood, for knots, cracks, splits and cuts. Framing lumber often needs only about 10%.
Related tools
- Deck Calculator — boards, joists and posts for a deck
- Fence Calculator — posts, rails and pickets for a fence
- Stair Calculator — stringers and treads for a staircase
- Unit Converter — inches, feet, cubic feet and cubic metres
How to use it
- Choose Feet & inches or Metres & cm
- Type the thickness, width, length and how many for the first board
- Use Add another board for each other size (it starts as a copy of the last one)
- Say whether your sizes are nominal or actual
- Add extra for waste and a price per board foot if you like
- Read the board feet and the cost, and press Copy the list
