Lumber Calculator

Unit system:

Choose Metric / SI for metres, millimetres, cubic metres, and litres, or Imperial for ft, in, board feet, and nominal US sizes.

Board size:

Presets fill width and thickness for the selected unit system; Custom keeps your manual dimensions.

Finished pieces:

Use the finished count before waste or bundle rounding.

Finished cut length:

Enter the required length for each finished board or part.

Finished cut length:

Enter the required length for each finished board or part.

Stock board length:

Set this to the store length so the calculator can estimate boards to buy and offcut.

Stock board length:

Set this to the store length so the calculator can estimate boards to buy and offcut.

Board width:

Use the measurement your lumber supplier uses for pricing.

Board width:

Use the measurement your lumber supplier uses for pricing.

Board thickness:

For rough lumber, use the thickness billed by the lumber yard.

Board thickness:

For rough lumber, use the thickness billed by the lumber yard.

Waste allowance: {{ formatPercent(waste_percent) }}

Typical quick estimates use 5-20%, depending on grade, knots, and cut layout.

Pricing basis:

Metric defaults to cubic-metre pricing; imperial defaults to board-foot pricing.

$ {{ price_basis === 'per_piece' ? '/ board' : (isMetric ? '/ m3' : '/ BF') }}

Saw kerf:

Default 0 keeps the original volume estimate neutral; set a blade width when repeated cuts matter.

Saw kerf:

Default 0 keeps the original board-foot estimate neutral; set 0.125 in for a common saw kerf.

Bundle size:

Use 1 for individual boards, or set a pack size if your supplier sells bundles.

boards

Tax / fee:

Default 0 keeps cost output as raw material cost.

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Metric	Formula	Value	Copy
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Check	Status	Detail	Copy
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A lumber estimate starts as a cut list and becomes a buying problem when the yard only sells full stock boards. Twelve identical parts may look like twelve boards, six boards, or more than twelve boards depending on stock length, saw kerf, defects, supplier pack size, and the way the quote prices the material.

The important split is finished material versus purchase material. Finished material is the wood that ends up in the project after cutting. Purchase material includes the full boards bought to make those pieces, plus length offcuts, sawdust from kerf, waste allowance, and any upward rounding caused by bundles or pack sizes.

Common lumber estimating factors and why they change the order
Estimating factor	Why it changes the order
Finished cut length	Controls how many repeated pieces fit on each stock board before leftover length becomes offcut.
Board width and thickness	Set the cubic volume or board-foot volume used for material and price comparisons.
Kerf	Removes a small length at each saw cut, which can reduce yield when stock length is tight.
Waste allowance	Adds boards for knots, splits, grade selection, mistakes, layout changes, and jobsite damage.
Bundle size	Rounds the final order to the supplier's selling multiple, which matters most on small jobs.

Board feet and cubic metres both describe volume, not cutting efficiency. A board foot is a lumber volume equal to a board 12 inches long, 12 inches wide, and 1 inch thick. Cubic metres use the same rectangular-volume idea in metric units. Neither unit decides whether a particular stock length can yield two, three, or four finished cuts.

Stock board diagram showing finished cuts, kerf gaps, and the remaining offcut.

Nominal and actual sizes cause many wrong takeoffs. A nominal 2 x 4 is a trade label, while the measured board may be smaller after surfacing and drying. Match the size basis to the supplier quote when estimating cost, and use measured dimensions when checking physical volume, shipping weight, or a tight fit.

A one-number lumber estimate is still a planning estimate. It does not grade boards, optimize a mixed cut list, account for grain direction, or know which offcuts can be reused later. It gives a first pass for repeated cut lengths, then leaves room for a real layout review before buying expensive material.

How to Use This Tool:

Start with the finished pieces the project requires, then match the stock length, board size, waste allowance, and price basis to the supplier quote.

Choose Metric / SI or Imperial / US customary. Metric uses metres, millimetres, cubic metres, and litres; imperial uses feet, inches, and board feet.
Pick a Board size preset or choose a custom size. If the supplier prices by nominal size, keep the matching preset; if you are checking measured material, enter the measured width and thickness.
Enter Finished pieces and Finished cut length. The tool models repeated pieces of one length, so split mixed-length jobs into separate estimates when the cuts differ materially.
Set Stock board length. The estimate must fit at least one finished cut on the stock board; otherwise the summary asks you to check the input.
Set Waste allowance, then open Advanced if you need a saw Kerf, a supplier Bundle size, or a Tax / fee percentage.
Choose the Pricing basis: per cubic metre in metric mode, per board foot in imperial mode, or per stock board in either mode.
Read Boards to buy in Purchase Takeoff, then check the Volume Ledger or Board Foot Ledger and the Cut Waste Plan before using the cost estimate.

Interpreting Results:

Boards to buy is the ordering number. It starts with the base stock boards needed for the finished pieces, adds the waste allowance, and rounds the result to the bundle size. The summary also reports purchase volume or board feet and estimated cost from the selected price basis and any tax or fee percentage.

Pieces per stock board is the first yield check. A value of 1 means every finished piece consumes a separate stock board.
Purchase volume or Purchase board feet includes rounded stock boards, not just installed material.
Length offcut shows material left after the repeated cuts and kerf. It may be useful on a real job, but it is not counted toward the required finished pieces.
Waste and bundle allowance explains the extra material beyond the base stock-board count.
Face coverage is a surface-area cross-check, not a substitute for length-by-length cutting review.

Do not treat a low waste number as proof that the order is ready. Defects, grain selection, board straightness, store availability, and mixed-length reuse can all change the final purchase. Use the allocation chart as a volume breakdown, then verify the actual cut layout when material cost or availability matters.

Technical Details:

Lumber takeoff combines rectangular volume with one-dimensional cutting yield. Volume says how much wood a board represents for pricing and comparison. Cutting yield says how many equal-length finished pieces fit into each stock board after the saw blade removes material between repeated cuts.

In imperial lumber buying, board-foot tally often uses thickness and width as billed by the supplier and length as the actual board length. In metric estimates, cubic volume uses thickness, width, and length after conversion to metres. The calculation is most reliable when the entered size basis matches the supplier quote.

Formula Core:

Stock-board volume is a rectangular solid. Board feet are the same volume expressed in the traditional lumber unit.

\begin{array}{lll} V_{stock} & = & T \times W \times L_{stock} \\ BF & = & \frac{T_{in} \times W_{in} \times L_{ft}}{12} \end{array}

Cut yield uses the finished cut length, stock length, and kerf. Adding kerf to both sides of the ratio is a compact way to model kerf between pieces without requiring an extra kerf after the last cut.

\begin{array}{lll} P & = & ⌊ \frac{L_{stock} + K}{L_{cut} + K} ⌋ \\ B_{base} & = & ⌈ \frac{N}{P} ⌉ \\ B_{buy} & = & ⌈ \frac{⌈ B_{base} \times (1 + A) ⌉}{G} ⌉ \times G \end{array}

Lumber formula symbols and meanings
Symbol	Meaning	Source in the estimate
`N`	Number of finished pieces.	Finished pieces
`L_cut`	Finished length of each required piece.	Finished cut length
`L_stock`	Length of each board being purchased.	Stock board length
`K`	Saw kerf converted to the same length unit.	Saw kerf in Advanced
`A`	Waste allowance as a decimal rate.	Waste allowance
`G`	Bundle or pack size in boards.	Bundle size in Advanced

The base stock-board count is rounded up because a partial board cannot be bought or cut as a full board. Waste is applied after that base count, then rounded up again. Bundle rounding is last, so a small one-board shortfall can become several extra boards when the pack size is larger than one.

Validation and interpretation boundaries for lumber estimates
Boundary	Rule	Why it matters
Positive dimensions	Piece count, cut length, stock length, width, and thickness must be greater than zero.	Zero or negative values cannot describe a real board or cut.
At least one cut fits	`P` must be at least `1`.	A stock board shorter than the finished cut cannot supply the part.
Waste range	The visible waste control runs from `0%` to `40%`.	Higher values reserve more material for selection and mistakes, but also increase the buy count.
Cost basis	Cost multiplies either purchase cubic metres, purchase board feet, or boards to buy.	The price field must match the quote, or the final dollar estimate will be wrong even when quantities are right.

For a substitution check, suppose 24 pieces are each 0.9 m long and the stock board is 3.6 m with no kerf. The yield is floor((3.6 + 0) / (0.9 + 0)) = 4 pieces per board, so the base count is ceil(24 / 4) = 6. With 10% waste and a 2-board bundle, the waste-adjusted count is ceil(6 x 1.10) = 7, and bundle rounding makes Boards to buy equal 8.

Advanced Tips:

Use Per stock board pricing when the quote is a shelf price per stick. Use the volume pricing options only when the supplier quote is per cubic metre or per board foot.
Set Saw kerf when repeated cuts come from longer stock. A small kerf can reduce Pieces per stock board when the length fit is tight.
Enter the supplier's Bundle size before reading Boards to buy. Bundle rounding happens after waste, so the final count can jump above the base board count.
Keep nominal presets for a nominal board-foot quote, and choose a custom size when measured width or thickness is the number that matters.
Use Lumber Volume Allocation or Lumber Board-Foot Allocation to see how much of the purchase is finished cutlist, length offcut, and waste or bundle allowance.
Leave Tax / fee at 0% for a material-only estimate, or enter the percentage when the quoted total should include added charges.

Worked Examples:

Metric Framing Run:

Twelve finished pieces at 2.4 m cut length from 2.4 m stock produce Pieces per stock board of 1. With 10% waste, Boards to buy rounds from 12 base boards to 14 boards. The Purchase volume is based on all 14 stock boards, while Finished cutlist volume covers only the installed pieces.

Board-Foot Quote:

An imperial estimate for nominal 2 x 6 boards uses Board feet per stock board as thickness in inches times width in inches times stock length in feet, divided by 12. If the yard quotes $4.25 per board foot, Estimated material cost follows purchase board feet. If the same yard gives a flat price per stick, switch Pricing basis to Per stock board.

Kerf Changes a Tight Layout:

Two 4 ft pieces seem to fit into an 8 ft stock board until saw kerf is included. With a 0.125 in kerf, the formula no longer fits two full cuts into exactly 8 ft, so Pieces per stock board falls to 1. Use longer stock, reduce finished length, or leave kerf at zero only when the supplier length already includes usable trim margin.

Cut Length Too Long:

A 3.0 m finished cut cannot come from a 2.4 m stock board. The summary changes to Check input and reports that stock board length must fit at least one finished cut length. Correct the stock length or split the job into an estimate for longer material.

FAQ:

Should I use nominal or actual dimensions?

Use the same basis as the quote when you are estimating cost. Use custom measured dimensions when physical volume, weight, or a tight fit matters more than the supplier's billing convention.

Why did the board count jump after I added kerf?

Kerf is counted between repeated cuts from the same stock board. When the stock length is already tight, even a small saw width can reduce Pieces per stock board and force more boards.

Why is purchase volume higher than finished volume?

Purchase volume includes offcuts, waste allowance, and bundle rounding. Finished volume counts only the material in the required finished pieces.

Can this handle mixed cut lengths?

The calculation models repeated pieces of one finished cut length. For a mixed cut list, run separate estimates for materially different lengths and review the combined layout before ordering.

What should I fix when the result says Check input?

Check that piece count, cut length, stock length, width, and thickness are greater than zero. If those look right, make the stock board long enough to fit at least one finished cut.

Glossary:

Board foot: A lumber volume equal to 12 inches by 12 inches by 1 inch, or an equivalent volume.
Stock board: The full board length and size purchased before it is cut into finished pieces.
Finished cut length: The required length of each repeated piece after cutting.
Kerf: The width of material removed by the saw blade during a cut.
Offcut: Leftover stock length after the required cuts and kerf have been removed.
Bundle size: The supplier pack multiple used to round the final board count upward.

References:

7 CFR 1217.4 - Board foot, Legal Information Institute.
Voluntary Product Standard PS 20-20: American Softwood Lumber Standard, National Institute of Standards and Technology, 2020.
Making Sure that Lumber Measures Up, National Institute of Standards and Technology, March 1, 2017.