Lumber Calculator
Work out the board feet in a stack of lumber from its thickness, width, length and the number of pieces. The tool also shows lineal feet and thousand board feet (MBF), adds an optional waste allowance, and estimates the order cost from a price in dollars per board foot, per piece, per lineal foot or per MBF.
Formula
Worked example
Ten 2x6 boards, each 8 ft long: (2 x 6 x 8) / 12 = 8 board feet per piece, x 10 = 80 net board feet (80 lineal feet). With 10% waste that is 88 board feet, 0.088 MBF. At 4.50 per board foot the material cost is about 396.
What a board foot is and how to calculate it
A board foot is a unit of lumber volume equal to 144 cubic inches, the amount of wood in a piece one foot long, one foot wide and one inch thick. To find it, multiply the thickness in inches by the width in inches by the length in feet, then divide by twelve. Multiplying that figure by the number of pieces gives the board feet for the whole order, which is the standard way hardwood lumber is measured and sold. Enter thickness and width in inches, millimetres or centimetres and length in feet, metres, centimetres or inches; the calculator converts everything before it works out the board feet.
Board feet, lineal feet and thousand board feet (MBF)
Suppliers quote lumber in several units, so the calculator shows all of them. Lineal feet (also called linear feet) measure only the total length you are buying, ignoring thickness and width, and are common for trim and dimensional framing. Board feet measure volume and are the norm for hardwood. Thousand board feet, written MBF, is simply board feet divided by one thousand and is how mills and wholesalers price truckload quantities. Because the tool reports board feet, lineal feet and MBF together, you can compare quotes from different yards no matter which unit each one uses.
Waste allowance, nominal sizes and estimating cost
Board-foot pricing almost always uses the nominal dimensions stamped on the lumber, not the slightly smaller actual size you get after planing: a nominal 2x4 actually measures about 1.5 by 3.5 inches but is still billed as a 2x4. Enter nominal numbers here to match how yards quote prices. Add a waste allowance, usually 10 to 15 percent, so you buy enough to cover knots, cracks, defects and trimming. Turn on the cost estimate and pick whether your price is per board foot, per piece, per lineal foot or per MBF; the calculator applies it to the matching quantity. The result is a material figure only, so add delivery, planing and sales tax before you set a budget.
Board feet in common dimensional lumber
| Size | 8 ft | 10 ft | 12 ft | 16 ft |
|---|---|---|---|---|
| 1x4 | 2.67 | 3.33 | 4.00 | 5.33 |
| 2x4 | 5.33 | 6.67 | 8.00 | 10.67 |
| 2x6 | 8.00 | 10.00 | 12.00 | 16.00 |
| 2x8 | 10.67 | 13.33 | 16.00 | 21.33 |
| 4x4 | 10.67 | 13.33 | 16.00 | 21.33 |
Board feet per single piece, using nominal thickness x width. Multiply by quantity.
Frequently asked questions
How do you calculate board feet?
Multiply thickness in inches by width in inches by length in feet, then divide by 12. For example a 2 in x 6 in x 8 ft board is (2 x 6 x 8) / 12 = 8 board feet. Multiply by the number of pieces for a full order, then add a waste allowance if you want a buy figure.
What is the difference between board feet, lineal feet and MBF?
Lineal feet (linear feet) measure only total length and ignore thickness and width. Board feet measure volume, so they account for thickness and width too. MBF means thousand board feet, just board feet divided by 1000, and is how mills price bulk loads. This calculator shows all three so you can match any supplier quote.
Should I use nominal or actual dimensions?
Use nominal dimensions, the size the lumber is sold as, such as 2x4. Board-foot pricing is based on nominal size, even though a planed 2x4 actually measures about 1.5 by 3.5 inches. That is the convention this calculator follows.
How much extra lumber should I buy for waste?
A waste allowance of about 10 to 15 percent is typical for project lumber to cover knots, cracks, splits and trimming cuts. Set the waste field and the calculator adds it to both the board feet and the number of pieces you should order.