A board-foot total tells you the billed volume of a lumber order. Enter the board's thickness, width, length, and piece count, and the calculator returns the measured board feet with per-piece, MBF, and cubic-metre equivalents. A planning allowance and an optional price per board foot stay as separate stages you control.
How many board feet do you need?
You need the measured board feet of every board in the order. The calculator multiplies thickness by width by length, divides by 12, and multiplies by the piece count. Metric entries convert exactly first: millimetres divided by 25.4 and metres divided by 0.3048.
The planning allowance starts at 0%, so the first result stays a checkable measurement. Enter a percentage only when the cut plan, grade, or project record supports it, and enter a price per board foot only when you have a current quote.
Record measured board feet first, the planning total second, and the supplier-rounded order quantity last. Each stage has a different source and can change for a different reason.
| Result | Calculation | What you must confirm |
|---|---|---|
| Board feet per piece | Thickness × width × length ÷ 12 | Dimensions entered and the unit system |
| Measured total | Per-piece board feet × piece count | Piece count and one uniform size per run |
| Planning total | Measured total × (1 + allowance ÷ 100) | Reason and evidence for the allowance |
| Estimated order cost | Planning total × entered price per board foot | Quoted price, size basis, and currency |
When should you use this board foot calculator?
Use it for one uniform board size at a time. Run the calculator once per size and add the unrounded totals when an order mixes sizes.
| Project condition | Calculator method | Record to keep |
|---|---|---|
| One board size, several identical pieces | Enter thickness, width, length, and count | Size, count, and the ticket's size basis |
| Mixed order | Calculate each size separately, then add unrounded totals | Size-by-size table with matching labels |
| Metric stock or export order | Use metric mode; the calculator converts exactly | Original metric dimensions and the billed unit |
| Quote check against a supplier ticket | Enter the seller's billed dimensions, not your tape readings | Ticket, billed size, and any tally rule noted |
| Hardwood sold by quarter thickness | Convert 4/4, 6/4, 8/4 to inches (1, 1.5, 2) before entering | Quarter size and whether the yard bills green or net tally |
| Slab, wane, or irregular board | Do not use this formula; ask the yard for its tally method | The yard's tally method and the board's identity |
The Material Conversion hub collects this calculator with the aggregate weight-volume converter and the board-foot guide cluster.
Which measurements do you need?
You need thickness, width, length, and the number of identical pieces. Measure in the units printed beside the fields and record where each number came from.
Thickness and width
Enter the size the seller bills, not necessarily what your tape shows. The American Softwood Lumber Standard PS 20 defines nominal size as the label designation and states that it does not reflect the dressed size, so a dry 2x4 bills at 2 by 4 inches even though it measures about 1.5 by 3.5 inches after surfacing. Computing from dressed boards gives a smaller number that will not match the yard's ticket. The board-foot guide explains the nominal-versus-actual distinction in full.
Length
Enter length in feet in imperial mode or metres in metric mode. Hardwood export tally practice rounds lengths down to the nearest whole foot, so confirm whether the ticket already reflects a rounded length before entering your own measurement.
Piece count
Count only identical pieces in one run. Different sizes need separate runs, and adding unrounded per-size totals keeps each size checkable.
Quarter thickness notation
Hardwood thickness is written in quarters of an inch: 4/4 is 1 inch, 5/4 is 1.25 inches, 6/4 is 1.5 inches, 8/4 is 2 inches, 10/4 is 2.5 inches, 12/4 is 3 inches, and 16/4 is 4 inches. These are nominal rough-sawn sizes, so confirm the yard's billed thickness before calculating.
What formula does the calculator use?
The calculator converts metric entries to inches and feet, then applies the American Hardwood Export Council formula. It retains full JavaScript precision during the calculation and displays board feet to 2 decimal places.
Board feet = thickness (in) × width (in) × length (ft) ÷ 12
Board feet = thickness (in) × width (in) × length (in) ÷ 144
Surface measure = width (in) × length (ft) ÷ 12; board feet = surface measure × thickness (in)
Measured total = per-piece board feet × piece count
Planning total = measured total × (1 + allowance % ÷ 100)
| Displayed conversion | Relationship | Calculator use |
|---|---|---|
| Inches to millimetres | 1 in = 25.4 mm exactly | Metric thickness and width conversion |
| Feet to metres | 1 ft = 0.3048 m exactly | Metric length conversion |
| Board feet to cubic inches | 1 BF = 144 in³ | Unit definition check |
| Board feet to cubic feet | 1 BF = 1/12 ft³ | Imperial volume comparison |
| Board feet to cubic metres | 1 BF = 0.0023597 m³ | Metric equivalent display |
| 1,000 board feet (1 MBF) | 2.36 m³ | Bulk quote comparison (AHEC rounded figure) |
| Cubic metres to board feet | 1 m³ = 424 BF | Metric stock to board feet (AHEC rounded figure) |
The inch, foot, and board-foot relationships come from the AHEC measurement page. The metric conversion factors are the exact defined relationships in the NIST Guide to the SI. Unit switching converts populated dimensions, clears the displayed result, and requires a fresh calculation in the selected units.
Worked imperial example
An order lists 6 pieces of 2x8, each 12 feet long, at nominal billed size.
- Per-piece board feet: 2 × 8 × 12 ÷ 12 = 16.
- Measured total: 16 × 6 = 96 BF.
- Thousand-board-feet equivalent: 96 ÷ 1,000 = 0.096 MBF.
- Metric equivalent: 96 × 0.0023597 = 0.2265 m³.
Measured result: 96 board feet. A user-entered 10% allowance gives a separate planning total of 105.6 BF. Cost remains blank until a quoted price per board foot is entered.
Worked metric example
An export buyer measures 10 boards at 50 mm thick, 150 mm wide, and 3.6 m long.
- Thickness in inches: 50 ÷ 25.4 = 1.9685.
- Width in inches: 150 ÷ 25.4 = 5.9055.
- Length in feet: 3.6 ÷ 0.3048 = 11.8110.
- Per-piece board feet: 1.9685 × 5.9055 × 11.8110 ÷ 12 = 11.44.
- Measured total: 11.44 × 10 = 114.42 BF.
Measured result: 114.42 board feet, which is 0.27 m³ of wood. The thousand-board-feet equivalent is 0.114 MBF.
How do tally rules change the board feet on a ticket?
Hardwood export tallies round board widths to the nearest whole inch, alternating up and down when a width falls exactly on the half inch, and always round lengths down to the nearest whole foot. A board 5.25 inches wide and 8.5 feet long tallies as 5 inches by 8 feet. These are the AHEC-documented bundle tally rules; a yard's ticket may note its own rule, so read it before entering dimensions.
Kiln drying adds another documented gap. Lumber sold on the gross (green) tally is measured before drying, and the buyer can expect about 7% less board feet after kiln shrinkage. Ask the yard whether the quote uses green or net tally before comparing it with a measured stack.
Enter the seller's billed dimensions when the task is a quote check, and enter your own verified measurements when the task is confirming what arrived. Note which basis you used; the two numbers answer different questions.
How should allowance be recorded?
The allowance field changes the planning total by the percentage you enter. It starts at 0%. Use a value only when defects, offcuts, the cut plan, grading rules, or a project requirement support it.
Write down the reason. Defects, cutting waste, tally rounding, and supplier rounding describe different causes, and separate records let a reviewer change one assumption without changing the measured total.
| Adjustment | Where it belongs | Evidence to record |
|---|---|---|
| Defects and wane to cut away | Planning allowance | Grade, species, and expected clear yield |
| Offcuts from the cut plan | Planning allowance | Cut list and expected usable percentage |
| Tally rounding (hardwood export) | Note beside measured total | Yard's tally rule and rounded dimensions |
| Supplier minimum or increment | Final order rounding | Current quote and selling unit |
| Commercial contingency | Budget record | Named risk, owner, amount, and approval |
How do you compare prices per board foot?
Divide a board's quoted price by its board-foot count to get the price per board foot, then compare that figure across suppliers. Board feet put boards of different thickness, width, and length on one scale.
Compare like with like. If one yard quotes on nominal size and another on actual size, convert both to the same basis first, or the cheaper-looking board may not be cheaper. Record which basis each quote used.
Example: 12 pieces of 1x6 at 8 feet hold 48 measured board feet. A 10% planning allowance gives 52.80 BF, and a $2.50 per-board-foot quote prices the planning total at $132.00. The measured 48 BF stays the checkable quantity if the allowance or the price changes.
Common board foot mistakes
- Entering dressed size when the yard bills nominal, or nominal when the check needs actual.
- Entering length in inches in a feet field, or mixing millimetres and centimetres.
- Rounding each board's board feet before multiplying by the piece count.
- Applying one allowance percentage across board sizes with different defect and offcut rates.
- Comparing price-per-board-foot quotes computed on different size bases.
- Treating board feet as a weight measure; it is a volume unit and species does not change the count.
- Using board feet for sheet goods or moulding sold by the square or lineal foot.
- Ignoring the ~7% kiln shrinkage when hardwood is sold on the green tally.
Questions about board feet
Is a board foot the same as a linear foot?
A linear foot measures length only: 12 inches of board, whatever its width and thickness. A board foot measures volume: a board 1 foot long, 1 foot wide, and 1 inch thick. Use board feet when wood volume sets the price.
What does MBF mean?
MBF means 1,000 board feet. Mills and large orders use it for bulk pricing; at $800 per MBF, the price is $0.80 per board foot.
Does thickness change the board feet?
Yes. Board feet equal surface measure times thickness, so a 2-inch board tallies twice the board feet of a 1-inch board with the same width and length.
Can this calculator choose the board size?
The calculator uses the dimensions you enter. The project design, span tables, drawings, or responsible person determine the required size.
What about slabs, wane, or irregular boards?
The formula assumes a rectangular section. Irregular stock needs the yard's own tally method; record that method with the quantity.
Does species change the board-foot count?
No. A board foot is a volume unit, so oak and pine boards of the same dimensions hold the same board feet. Species changes weight and price, not the count.
Can one run handle a mixed order?
Run each uniform size separately and add the unrounded measured totals. Keep a size-by-size table so each line stays checkable against its ticket line.
Sources and scope
- AHEC: Grading sawn lumber (Measurement): board-foot definition, the W × L × D ÷ 12 formula, surface measure, export tally rounding rules, quarter-sawn thickness notation, green-versus-net kiln tally (~7%), and the 1 MBF = 2.36 m³ and 1 m³ = 424 BF conversion factors; accessed 18 October 2026.
- NIST Guide to the SI, Appendix B: exact metric and US customary conversion relationships; accessed 28 July 2026.
- NIST Handbook 44 (2026), Appendix C: cubic-foot, cubic-inch, cubic-yard, litre, and cubic-metre volume relationships; accessed 28 July 2026.
Source scope: AHEC supports the formula, the tally rules, and the board-foot conversion factors. NIST supports the exact inch, foot, and volume relationships behind the metric conversion path and the 0.0023597 m³ figure. Nominal-versus-dressed guidance follows the American Softwood Lumber Standard PS 20 as documented in the site's board-foot guide. Supplier tickets, drawings, grading rules, and responsible project people control the billed size, tally basis, order, and work plan.
Review note: Calculation logic and independent automated fixtures passed internal review. Saleem Sial is the research and editorial owner. Waseem Sial's external review remains ongoing. The published page is indexable.
