How do you calculate board feet?
A board foot measures lumber volume. The Government of Canada’s unit definition is 12 inches × 12 inches × 1 inch, giving 144 cubic inches. Wood-Mizer’s official explanation gives the formula with thickness and width in inches and length in feet.
Converting a length of L feet to inches gives 12L. Dividing T × W × 12L by 144 simplifies to T × W × L / 12. Quantity multiplies that per-piece result. Different sizes or rates belong on separate rows.
BF per piece = T(in) × W(in) × L(ft) / 12
Row BF = BF per piece × quantity
Row cost = row BF × entered USD / BF
Total BF and cost = sum of the corresponding rows
Length stays in feet: 8.5 is 8 feet 6 inches. If your tape measure shows 96 inches, enter 8 feet. Fractions such as 3/4 are accepted for dimensions; the tool does not read feet-and-inches notation such as 8′ 6″.
Actual volume and a seller’s billing dimensions can differ
Use measured dimensions to estimate physical volume. For a purchase estimate, ask the seller which thickness, width, length and tally rules its price uses. Nominal, roughsawn and surfaced dimensions may describe different inputs. The calculator uses the numbers you enter without silently changing them.
For example, Hardwood Industries describes its own thickness-rounding convention. That seller-specific behavior is not applied here. Select the dimension basis above as a label for your record, then enter the appropriate sizes yourself.
| Entered basis | Thickness × width × length | Quantity | Total BF | At example $5 / BF |
|---|---|---|---|---|
| Measured-size example | 0.75 in × 6 in × 8 ft | 4 | 12 | $60.00 |
| Hypothetical seller-specified thickness | 1 in × 6 in × 8 ft | 4 | 16 | $80.00 |
The second row is a stated arithmetic assumption, not a rule for every seller. Neither example supplies a current lumber price.
Keep the material subtotal separate from cutting yield
Every row has its own editable price in USD per BF. The initial $5 rate demonstrates the calculation. Replace it with a quoted rate for your material and dimension basis. Zero is valid; a blank rate remains incomplete.
The result does not add defects, kerf, trim, milling, waste, taxes or delivery. It does not prove that the required parts fit the boards. Keep any purchasing allowance and quoted extra charges separate, and check the actual cutting layout before buying.
Displayed BF values round to four decimal places; cost rounds to cents after summing unrounded row estimates. A supplier that rounds each line or uses a different tally basis may produce a different invoice. All calculator inputs are processed locally in your browser.
Board foot calculator FAQ
How do you calculate board feet with length in feet?
Multiply thickness in inches by width in inches by length in feet, then divide by 12. Multiply by the number of identical boards for the row total: BF = T × W × L × quantity / 12.
Is a board foot the same as a linear foot?
No. A linear foot measures length. A board foot measures a volume of 144 cubic inches. The same length of two boards can contain different board footage when their thickness or width differs.
Should I use actual dimensions or nominal lumber sizes?
For physical volume, enter measured thickness, width and length. For an invoice estimate, enter the dimensions and price basis the seller uses. This calculator does not convert nominal sizes or apply seller-specific tally rounding.
Is the initial $5 per BF a current lumber price?
No. It is an editable example rate, not a market price or supplier quote. Replace each row’s rate with your own USD price per board foot. Zero is allowed; a blank price is incomplete.
Does the cost include waste, milling, tax or delivery?
No. Cost is each row’s calculated board footage multiplied by its entered USD rate, summed across rows. Add any separately quoted charges or purchasing allowance to your own budget. The calculator does not infer a waste percentage or cutting yield.
Can I enter fractions and decimal feet?
Thickness, width and length accept decimals or fractions such as 3/4 and 8 1/2. Length is always feet, so 8.5 means 8 feet 6 inches. Quantity must be a positive whole number; unit price uses decimal USD.
Sources
- Government of Canada — board foot unit definition, section 1
The unit definition is 12 inches × 12 inches × 1 inch, which is 144 cubic inches. This page cites that dimensional definition only.
- Wood-Mizer — What is a Board Foot?
The manufacturer’s calculation uses thickness and width in inches, length in feet, and divides by 12; quantity multiplies the result.
- Hardwood Industries — Board Footage Calculator, notes 1–3
The seller explains nominal or roughsawn thickness and its own thickness-rounding convention. This calculator does not automatically apply that seller’s tally rules.