How to use this calculator
- 1Count the pieces of one size. For a mix of sizes, work out each size on its own and add each one to your project list.
- 2Enter the thickness and width. For US softwood use the nominal size (2 × 4, 2 × 6); for rough hardwood use the thickness in quarters (4/4 = 1 in); for metric timber use the size on the label.
- 3Enter the length of each piece.
- 4Optional: under Prices, type your supplier's price and choose whether it is per board foot, per m³, per piece or per metre or foot, to see the total.
The formula
- 01Board feet per piece = thickness (in) × width (in) × length (ft) ÷ 12
- 02Total board feet = board feet per piece × number of pieces
- 03Volume = pieces × thickness × width × length
- 041 board foot = 144 in³ = 0.00236 m³, so 1 m³ ≈ 423.8 board feet
A board foot is a piece of wood 1 inch thick, 12 inches wide and 1 foot long, which is 144 cubic inches. It is the standard unit for buying hardwood, and softwood is traded by the thousand board feet (MBF) in the US and Canada. Because thickness and width are in inches but the length is in feet, the formula divides by 12 — or by 144 if you measure the length in inches too.
In the US, board feet for softwood lumber are counted from the nominal size, not the smaller size after drying and planing (NIST PS 20, section 2.2). An 8 ft 2 × 6 is 8 board feet even though the wood is only about 1½ × 5½ in. Rough hardwood is counted on its rough thickness in quarters of an inch. In Europe and other metric countries, timber is usually sold by its actual size — by the cubic metre, per piece or per running metre.
Converting board feet to cubic metres is only exact when both use the same sizes. A board-foot figure from nominal sizes, converted to m³, overstates the wood you really get — the NIST standard warns about exactly this.
Worked example
10 pieces of 2 in × 6 in lumber, each 8 ft long, come to 8 board feet each and 80 board feet in total.
That is 6.67 ft³ of wood by nominal size. Laid end to end it is 80 ft of lumber — the linear feet a store counts, which is not the same as board feet.
Tips before you buy
- Softwood is often quoted per thousand board feet (MBF). Divide an MBF price by 1,000 and enter it as a price per board foot.
- Rough hardwood gets thinner when you plane it: as a rule of thumb 4/4 stock finishes at about ¾ in and 5/4 at about 1 in, so buy the rough thickness your finished parts need.
- Allow extra for knots, splits and offcuts. How much depends on the grade and your cutting list, so plan the cuts first and then add a margin.
- When a store sells by the piece, compare it with a lumber yard by working out the price per board foot: price per piece ÷ board feet per piece.
- For decks and fences, the decking and fence calculators count the pieces for you — enter those counts here to price them by volume.
Frequently asked questions
How do you calculate board feet?
Multiply the thickness in inches by the width in inches and the length in feet, then divide by 12. An 8 ft long 2 × 6 is 2 × 6 × 8 ÷ 12 = 8 board feet. If you measure the length in inches as well, divide by 144 instead.
Do you use nominal or actual size for board feet?
For US softwood lumber, the nominal size: that is how the American Softwood Lumber Standard (NIST PS 20) defines board measure, and how yards price it. Rough hardwood is counted on its rough thickness (4/4, 8/4). If you want the real volume of wood, enter the measured size instead.
How many board feet are in a cubic metre?
About 423.8. One board foot is 144 in³, which is 0.00236 m³. Remember that a board-foot figure worked out from nominal sizes is more than the real volume of wood, so converting it to cubic metres overstates the timber.
What is the difference between board feet and linear feet?
Linear feet measure length only. Board feet measure volume, so thickness and width count too: a 1 × 12 and a 2 × 6 both have 1 board foot per linear foot, while a 2 × 4 has about 0.67.
What do 4/4 and 8/4 mean?
Hardwood thickness is given in quarters of an inch of rough, unplaned thickness: 4/4 is 1 in, 5/4 is 1¼ in and 8/4 is 2 in. Board feet for rough hardwood are counted on that rough thickness.
How do I price timber sold per cubic metre or per metre?
Under Prices, type the price and choose "per m³"; the calculator multiplies it by the volume. For timber sold per running metre, choose "per m" instead ("per ft" on the imperial setting), and it multiplies the price by the total length.
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Sources
- NIST Voluntary Product Standard PS 20-20, American Softwood Lumber Standard (board measure, §2.2; nominal and dressed sizes)
- Rockler: the quarter system of hardwood thickness (4/4 = 1 in rough)
Formulas last reviewed: September 30, 2026 ·How we check our formulas