Board Foot Calculator
This calculator works out the volume of timber in board feet, the unit used across North America to measure and price rough-sawn lumber and hardwoods, and one you will still meet in New Zealand when buying imported or specialty timber. Enter the thickness, width and length of a single board, in inches and feet or in millimetres and metres, then add the number of pieces you need. You can also enter a price per board foot and pick a waste allowance from 0 to 20 percent to cover off-cuts and trimming. The calculator applies the standard board foot formula, thickness times width times length divided by 12, and returns the board feet for one piece, the total board feet for all pieces including waste, the equivalent volume in cubic metres, and an estimated cost. A breakdown below the results also shows cubic inches, cubic feet, and costs with and without waste, so you can check every step. Switch between imperial and metric inputs at any time and the figures update instantly. Use it to quote a timber order, compare suppliers who price in board feet, or convert an order into cubic metres for local pricing. Timber dimensions can vary slightly due to dressing, moisture content and sawing tolerance, so treat the result as an estimate and confirm final quantities and pricing with your timber supplier before ordering.
1. Board Dimensions
2. Quantity and Cost
Volume Breakdown
Conversions and Cost
How to Calculate Board Feet
A board foot is a unit of timber volume used primarily in North America for measuring and pricing rough-sawn lumber and hardwoods. The formula is straightforward:
For example, a board that is 1 inch thick, 6 inches wide and 8 feet long contains: (1 × 6 × 8) ÷ 12 = 4 board feet.
If you have 10 such boards, the total is 40 board feet (before any waste allowance).
Worked Example (Default Values)
Using the default inputs (imperial, 1 inch thick, 6 inches wide, 8 feet long, 10 pieces, 10% waste, $5.00 per board foot):
| Step | Calculation | Result |
|---|---|---|
| Board feet per piece | (1 × 6 × 8) ÷ 12 | 4.00 BF |
| Board feet for 10 pieces | 4.00 × 10 | 40.00 BF |
| 10% waste allowance | 40.00 × 1.10 | 44.00 BF |
| Total volume in cubic metres | 44.00 × 0.002359737 | 0.104 m³ |
| Estimated cost (incl. waste) | 44.00 × $5.00 | $220.00 |
Using Metric Dimensions
If your timber is measured in millimetres and metres (as is standard in New Zealand), convert to inches and feet first, or use the metric mode in this calculator. The conversion factors are:
- 1 inch = 25.4 mm, so thickness in inches = thickness in mm ÷ 25.4
- 1 foot = 0.3048 m, so length in feet = length in metres ÷ 0.3048
- Width in inches = width in mm ÷ 25.4
The metric mode in this calculator handles these conversions automatically.
Common Timber Sizes in Board Feet
| Thickness | Width | Length | Board Feet per Piece |
|---|---|---|---|
| 1 in | 4 in | 8 ft | 2.67 BF |
| 1 in | 6 in | 8 ft | 4.00 BF |
| 1 in | 8 in | 8 ft | 5.33 BF |
| 1 in | 6 in | 12 ft | 6.00 BF |
| 2 in | 4 in | 8 ft | 5.33 BF |
| 2 in | 6 in | 8 ft | 8.00 BF |
| 4 in | 4 in | 8 ft | 10.67 BF |
Board Feet vs Cubic Metres
In New Zealand, structural framing timber is typically sold by lineal metre or cubic metre, not board feet. However, hardwoods, specialty timbers and imported North American lumber (such as Douglas fir, cedar and redwood) are still priced in board feet. One board foot equals 0.002359737 cubic metres. To convert cubic metres to board feet, divide by 0.002359737 (or multiply by 423.776).
Waste Allowance
When purchasing timber for a project, it is good practice to add a waste allowance to account for off-cuts, defects, and end-trimming. A 10% allowance is typical for prepared (dressed) timber. For rough-sawn stock or where significant cutting is required, 15 to 20% is more appropriate. The waste percentage in this calculator is applied on top of the net quantity required.
Related Calculators
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- Timber Board Feet and Lengths Calculator
- Area Conversion Calculator
- Concrete Bags Needed Calculator
- Cost of a Deck or Fence All-In Calculator
Method: Board foot formula: BF = (T″ × W″ × L') ÷ 12, where T is thickness in inches, W is width in inches and L is length in feet. Cubic metre conversion uses 1 BF = 0.002359737 m³ (exactly 144 cubic inches × (0.0254 m/in)³). Metric inputs are converted to inches and feet before applying the formula.
This calculator is for estimating purposes. Timber dimensions may vary due to dressing, moisture content and sawing tolerance. Always confirm quantities with your timber supplier before ordering. Prices are indicative only and vary by species, grade and supplier.