Lumber weight and price calculator

Before you optimise a cutting list, it pays to know how much lumber you actually need, what it will weigh, and what it will cost. This guide walks through the formulas so you can size up a project in minutes and feed accurate numbers into the OptimalLayout cut optimizer — the two calculations belong together, because knowing the volume is what tells you how many sheets or boards to buy in the first place.

1. Board feet — the universal lumber unit

One board foot is a piece 1 inch thick, 12 inches wide and 12 inches long (144 in³ of nominal volume). The formula is:

Board feet = (Thickness in × Width in × Length ft) ÷ 12

Example: a 2×4 that is 8 ft long → (2 × 4 × 8) ÷ 12 = 5.33 board feet. Multiply by your price per board foot to get the cost.

Two subtleties trip people up. First, hardwood dealers quote nominal thickness in quarters ("4/4", "8/4") — a 4/4 board is sold as 1" thick even after it is planed to ¾". Always calculate BF from the nominal size, not the finished size. Second, when a board is wider than 12" the width goes into the formula as inches, not feet: a 14" × 8 ft × 1" board is (1 × 14 × 8) ÷ 12 = 9.33 BF, not 0.78.

2. Volume in metric (m³)

Outside North America, lumber is usually sold by the cubic metre. Convert all three dimensions to metres and multiply:

Volume (m³) = Thickness × Width × Length (all in metres)

Example: 38 × 89 × 2400 mm → 0.038 × 0.089 × 2.4 = 0.00812 m³. A m³ of construction-grade softwood typically costs €350–€600 depending on species, region and grade; European oak runs €1,200–€2,000 per m³ for kiln-dried squared stock.

For sheet goods the same formula works, but it is easier to price per sheet. A pack of 50 sheets of 18 mm MDF at 2440 × 1220 contains 50 × 0.018 × 2.44 × 1.22 ≈ 2.68 m³ of material — useful when you compare a bulk pack price against per-sheet retail.

3. Weight — density × volume

Weight matters for shipping, for floor loading, and for working out whether you can lift a sheet on your own. Multiply volume by the species density:

• Pine / SPF: ~470 kg/m³ (29 lb/ft³)
• Douglas fir: ~530 kg/m³ (33 lb/ft³)
• European oak: ~720 kg/m³ (45 lb/ft³)
• Hard maple: ~705 kg/m³ (44 lb/ft³)
• Walnut: ~610 kg/m³ (38 lb/ft³)
• Birch plywood: ~680 kg/m³ (42 lb/ft³)
• Softwood plywood: ~550 kg/m³ (34 lb/ft³)
• MDF: ~750 kg/m³ (47 lb/ft³)
• Particle board / MFC: ~680 kg/m³ (42 lb/ft³)
• OSB/3: ~640 kg/m³ (40 lb/ft³)

A full 18 mm MDF sheet (2440 × 1220 mm) therefore weighs about 0.018 × 2.44 × 1.22 × 750 ≈ 40 kg — a two-person lift. A 22 mm OSB tongue-and-groove floor sheet at 2400 × 600 comes in around 20 kg, easy for one. Always check before you order how many sheets your van can carry legally — a 50-sheet pack of 18 mm MDF is two tonnes, well beyond a 3.5 t van's payload once the driver is inside.

For green (unseasoned) softwood, add roughly 30 % to the kiln-dried density above until the wood has stabilised at 12–15 % moisture content.

4. Price — three ways to quote it

• Per board foot (US hardwood dealers): Total = board feet × $/BF. Typical: FAS oak $4–7, walnut $10–14, hard maple $5–8 per BF as of 2025.
• Per linear foot or metre (dimensional softwood): Total = length × price/length. A 38 × 89 mm stud in Europe is €2–4 per linear metre.
• Per sheet (plywood, MDF, OSB): Total = sheets needed × price/sheet. 18 mm melamine 2800 × 2070 runs €40–70 depending on decor.

Always add 10–15 % for defects, offcuts and the saw kerf — even with a good cutting list, real sheets have grain, knots and factory-cut edges you will trim away. On expensive hardwood, some shops add 20 %; on cheap softwood 10 % is usually enough.

5. Worked example: a small bookshelf

Say you are building a 1800 × 900 × 300 mm bookshelf from 18 mm birch plywood. The parts list is:

• 2 × sides: 1800 × 300 mm
• 5 × shelves: 900 × 280 mm (280 to leave a 20 mm rebate at the back)
• 1 × top: 936 × 300 mm
• 1 × back: 1800 × 900 mm × 6 mm ply

Total face area of 18 mm parts ≈ 2.86 m². One sheet of 2440 × 1220 mm is 2.98 m², so at first glance one sheet ought to be enough. In practice, because parts do not tile perfectly and the kerf eats material, you will need two sheets — which the optimizer will confirm in a second, with a diagram showing exactly where each part comes from.

Weight: 2 × (0.018 × 2.44 × 1.22 × 680) ≈ 73 kg for both sheets — a two-person lift into the workshop. Cost at €70/sheet for birch ply plus €25 for the 6 mm back = ~€165 in materials before glue, edgebanding and finish.

6. Feed the numbers into OptimalLayout

Once you know the part sizes, open the cut optimizer and enter your base sheet or board dimensions plus each part. The optimizer returns the minimum number of sheets, total cut length and a labelled diagram — so the lumber you actually buy matches your estimate, with as little waste as possible.

Quick reference

• Board feet = (T_in × W_in × L_ft) ÷ 12
• Volume m³ = T_m × W_m × L_m
• Weight kg = Volume m³ × density kg/m³
• Add 10–15 % waste before ordering (20 % on hardwood)
• Use OptimalLayout to confirm the real sheet count

7. Moisture and movement

Wood is a hygroscopic material — it swells as it takes on humidity and shrinks as it dries. Kiln-dried furniture stock leaves the mill at 8–10 % moisture content; a workshop in a Dutch autumn easily runs 15 %. A 300 mm-wide oak panel can grow or shrink 3–4 mm across the grain between summer and winter, which is why solid-wood tops are attached with slotted fasteners and why plywood is a friend of the maker in a variable climate.

For pricing, remember two things: fresh-sawn (green) stock is heavier and cheaper per m³ than kiln-dried, but you cannot use it until it dries — budget 12 months per inch of thickness for air drying, or pay the kiln-drying premium.

8. Delivery, handling and van loads

The invoice is not the whole cost. Sheet materials are heavy and awkward, and the last 30 metres from the van to the workshop are what actually break your back. A short checklist for anything over 5 sheets:

• Confirm the merchant will deliver to the door, not just kerbside.
• Check your van's payload — a 3.5 t Sprinter typically carries ~1,200 kg once the driver is inside. A pack of 30 sheets of 18 mm MDF is 1,200 kg on its own.
• Ask for the pack strapped and shrink-wrapped; loose sheets slide and the top ones get corner-damaged.
• Have a second person and either a panel trolley or two rope loops ready for the two-person carry.

9. Sanity-check with a rule of thumb

Every calculation deserves a sanity check. Two useful ones:

• 1 m³ of softwood ≈ 470 kg. If your weight estimate for a stack of pine is far off that per cubic metre, the arithmetic is wrong somewhere.
• 1 sheet of 18 mm MDF ≈ 40 kg, 1 sheet of 18 mm birch ply ≈ 33 kg, 1 sheet of 18 mm melamine ≈ 37 kg. Multiply by sheet count for a quick load estimate.

Reference table