Timber Volume, Weight & Cost Calculator (Metric + Imperial)

A timber list can be described in several valid ways: cubic metres, cubic feet, board feet, linear metres, linear feet, or simply a number of pieces. The difficulty begins when dimensions arrive in one system, the supplier quotes in another, and transport planning needs an estimated weight.

The Timber Volume, Weight & Cost Calculator brings those quantities into one transparent workflow. It can start from member dimensions or from a known volume, then convert units, apply a waste allowance, estimate mass from a chosen density, and calculate material cost from a user-entered price.

It is an estimating tool, not a structural design tool. It does not select member sizes, verify loads or spans, check grades and connections, or confirm compliance with building codes.

What the calculator needs

There are two useful starting routes.

Route 1: dimensions and piece count

Enter the actual thickness, width, length, and number of identical pieces. For a mixed list, calculate each member group separately and add the results. Actual finished dimensions are normally safer than nominal names because planed, dried, and manufactured products may not match their nominal dimensions.

The calculator can also report total linear length. Linear length is count multiplied by piece length, but it is not volume. Two members can have the same length and very different cross-sections, weight, and cost.

Route 2: known volume

If a takeoff, supplier schedule, or model already gives a net volume, enter it directly.

The formulas behind the result

The core calculation uses SI units. Dimensions are converted to metres before volume is calculated:

Volume (m³) = count × thickness (m) × width (m) × length (m)

For multiple groups:

Total volume (m³) = sum of every group volume

The Bureau International des Poids et Mesures lists the cubic metre as the SI unit of volume and kilograms per cubic metre as the unit for mass density. Imperial outputs are conversions from the same underlying volume, which avoids maintaining two separate calculations.

NIST defines the international foot as exactly 0.3048 metres. It follows that:

1 ft³ = 0.028316846592 m³

1 m³ = 35.3146667 ft³, rounded

NIST Handbook 130 defines one board foot as the volume of a board 1 foot long, 1 foot wide, and 1 inch thick, equal to 144 cubic inches. Therefore:

1 board foot = 1/12 ft³ = 0.002359737216 m³

Board feet = volume (m³) ÷ 0.002359737216

A board foot is a volume unit, not a piece count. Purchasing conventions also matter: hardwood, softwood, rough, surfaced, and nominal stock may be measured or sold differently. Use the supplier’s stated basis for a quotation.

Waste is applied as an explicit planning allowance:

Purchase volume = net volume × (1 + waste percentage ÷ 100)

Estimating timber weight

Estimated mass is:

Mass (kg) = purchase volume (m³) × selected density (kg/m³)

Density is not one universal timber constant. The USDA Forest Products Laboratory explains that wood is hygroscopic: its moisture content changes with surrounding conditions, and both mass and volume depend on moisture content. Density also varies by species, product, and individual piece. Engineered timber may have a manufacturer-declared value that is more appropriate than a generic species value.

For that reason, the density field is an assumption. Prefer a supplier data sheet, product declaration, or project specification that states the density basis and moisture condition. The weight result is useful for early logistics and comparison, but it is not a certified shipping weight or lifting plan. Coatings, fixings, plates, packaging, and retained moisture can add mass.

Estimating material cost

The cost formula follows the unit used by the supplier:

Estimated material cost = billable quantity × user-entered unit price

If the quotation is per cubic metre, use purchase volume in cubic metres. If it is per cubic foot or board foot, use the corresponding converted quantity. If the supplier sells by piece, a volume-based price may not reproduce the quotation because stock-length rounding and minimum order quantities can dominate.

The calculator does not perform currency conversion. A value entered as 540 per m³ produces 540 in the same currency chosen by the user. It also does not claim to calculate total project cost. Unless the user adds them separately, the result excludes sales tax or VAT, delivery, treatment, machining, connectors, fasteners, labour, equipment, design, engineering, permits, foundations, finishes, and site overhead.

Worked metric example

Assume an already-specified list contains 12 timber members, each 120 mm thick, 200 mm wide, and 4.5 m long. These dimensions are an estimating example, not a sizing recommendation.

Convert millimetres to metres and calculate the net volume:

12 × 0.12 × 0.20 × 4.5 = 1.296 m³

The total linear length is:

12 × 4.5 = 54 m

With a 10% waste allowance:

1.296 × 1.10 = 1.4256 m³ purchase volume

At an assumed density of 470 kg/m³:

1.4256 × 470 = about 670 kg

At a user-entered material rate of 540 currency units per m³:

1.4256 × 540 = about 770 currency units

The same purchase volume is approximately 50.34 ft³ or 604.14 board feet. Those conversions do not change the wood; they only express the same volume in different units.

Worked imperial example

Assume a list contains 20 rough boards measuring 2 inches by 8 inches by 12 feet. Using the board-foot formula:

Board feet per piece = thickness (in) × width (in) × length (ft) ÷ 12

2 × 8 × 12 ÷ 12 = 16 board feet per piece

For 20 pieces:

20 × 16 = 320 board feet net

With a 12% waste allowance:

320 × 1.12 = 358.4 board feet

That equals approximately 29.87 ft³ or 0.8457 m³. At an assumed density of 520 kg/m³, the estimated mass is about 440 kg, or 970 lb. At a quoted rate of 4.25 currency units per board foot, the estimated material amount is 1,523.20 in that same currency.

Before ordering, confirm whether the supplier uses rough, surfaced, actual, or nominal dimensions and how board footage is rounded.

A practical checking sequence

A useful estimate should remain easy to audit:

• Use actual dimensions where available.

• Separate member groups with different sections, products, or densities.

• Match the density to the declared moisture condition.

• Match the cost basis to the supplier’s quotation unit.

• Apply waste visibly instead of hiding it in dimensions or price.

• Round to purchasable pieces or stock lengths only after the continuous volume is understood.

• Keep taxes, transport, fabrication, and other exclusions explicit.

The result should help prepare a conversation with a supplier or project team, not replace a verified takeoff, procurement quote, structural design, or lifting assessment.

From quick estimate to coordinated model

A transparent calculator is most useful early, when a designer or builder needs to test quantities without pretending the design is finished. Once the geometry is agreed, the next step is to keep member dimensions and quantities connected to the project model.

Use the calculator for a quick, auditable estimate. If you want to develop the timber geometry further, explore FrameVerk and follow its launch updates.

Sources

• Bureau International des Poids et Mesures, “SI Brochure: The International System of Units (SI), 9th edition,” updated 2026: https://www.bipm.org/en/publications/si-brochure

• National Institute of Standards and Technology, “NIST Guide to the SI, Appendix B: Conversion Factors,” accessed 30 July 2026: https://www.nist.gov/pml/special-publication-811/nist-guide-si-appendix-b-conversion-factors

• National Institute of Standards and Technology, “Handbook 130 — 2026, Uniform Regulation for the Method of Sale of Commodities,” 2026: https://www.nist.gov/document/2026-hb-130-section-iv-b

• USDA Forest Products Laboratory, Glass and Zelinka, “Chapter 4: Moisture Relations and Physical Properties of Wood,” 2021: https://research.fs.usda.gov/treesearch/62243