Woodworking & Carpentry · Calculator
Board Foot Calculator
Use this board foot calculator to get board feet per piece, the total for your whole stack, and what it will cost. It works for rough hardwood (4/4, 8/4) and dimensional lumber like 2x4s.
Your lumber
Lumberyards price dimensional lumber by nominal size, so a 2x4 counts as 2 in by 4 in even though it measures 1-1/2 by 3-1/2.
How to calculate board feet
A board foot is a unit of volume: 144 cubic inches, or a piece 1 inch thick, 12 inches wide and 12 inches long. To find board feet, multiply thickness by width by length in inches and divide by 144. If you measure length in feet, divide by 12 instead.
For rough hardwood, use the quarter thickness (4/4 = 1 inch, 8/4 = 2 inches) and the actual width of the board. Hardwood dealers measure each board and round width to the nearest inch.
For dimensional lumber, use the nominal size. A 2x6 is priced as 2 by 6 inches, even though it measures 1-1/2 by 5-1/2.
Nominal vs actual lumber sizes
A 2x4 is actually 1-1/2 inches by 3-1/2 inches. Drying and planing take the rest. Here are the common sizes, their actual dimensions, and how many board feet each one has per linear foot.
| Nominal | Actual size (in) | Bd ft per linear ft | 8 ft board | 10 ft board |
|---|---|---|---|---|
| 1x4 | 3/4 x 3-1/2 | 0.333 | 2.67 | 3.33 |
| 1x6 | 3/4 x 5-1/2 | 0.500 | 4.00 | 5.00 |
| 1x8 | 3/4 x 7-1/4 | 0.667 | 5.33 | 6.67 |
| 1x12 | 3/4 x 11-1/4 | 1.000 | 8.00 | 10.00 |
| 2x4 | 1-1/2 x 3-1/2 | 0.667 | 5.33 | 6.67 |
| 2x6 | 1-1/2 x 5-1/2 | 1.000 | 8.00 | 10.00 |
| 2x8 | 1-1/2 x 7-1/4 | 1.333 | 10.67 | 13.33 |
| 2x10 | 1-1/2 x 9-1/4 | 1.667 | 13.33 | 16.67 |
| 2x12 | 1-1/2 x 11-1/4 | 2.000 | 16.00 | 20.00 |
| 4x4 | 3-1/2 x 3-1/2 | 1.333 | 10.67 | 13.33 |
| 6x6 | 5-1/2 x 5-1/2 | 3.000 | 24.00 | 30.00 |
Hardwood thickness: the quarter system
Hardwood is sold by rough thickness in quarter inches. You pay for the full rough thickness even when you buy it surfaced, so a 4/4 board planed to 13/16 inch still counts as 1 inch thick for board feet.
If you plan to flatten and plane stock yourself, buy the next quarter up from your finished thickness. A 3/4 inch tabletop needs 4/4 lumber, and a 1-1/4 inch leg blank needs 6/4.
Breaking down long boards? A good miter saw makes quick work of crosscuts, and our table saw buying guide covers what matters for ripping hardwood.
| Quarter | Rough thickness | Surfaced (S2S) |
|---|---|---|
| 4/4 | 1 in | 13/16 in |
| 5/4 | 1.25 in | 1-1/16 in |
| 6/4 | 1.5 in | 1-5/16 in |
| 8/4 | 2 in | 1-3/4 in |
| 10/4 | 2.5 in | 2-1/4 in |
| 12/4 | 3 in | 2-3/4 in |
Tips for buying lumber by the board foot
- Bring a cut list, not just a total. Knowing your longest and widest parts keeps you from buying a pile of short, narrow boards that add up on paper but do not fit your project. Our cut list optimizer helps with sheet goods.
- Add waste before you buy. 15 to 20 percent is normal for rough hardwood. Figured woods and boards with sapwood you plan to cut away need more.
- Compare prices per board foot, not per board. Big box stores price per piece, which hides how much you are paying. Run their price through the calculator to compare with a lumberyard.
- Check moisture. Kiln-dried hardwood for furniture should read 6 to 8 percent moisture content.
Frequently asked questions
How many board feet are in a 2x4x8?
A 2x4x8 has 5.33 board feet. Lumberyards use the nominal size, so the math is 2 x 4 x 8 / 12 = 5.33, even though the board actually measures 1-1/2 by 3-1/2 inches.
How do you calculate board feet?
Multiply thickness (inches) by width (inches) by length (feet) and divide by 12. If you measure length in inches, divide by 144 instead. One board foot is 144 cubic inches.
What does 4/4 or 8/4 mean on hardwood?
It is rough thickness in quarter inches. 4/4 is 1 inch, 5/4 is 1-1/4 inches, 6/4 is 1-1/2 inches and 8/4 is 2 inches. Hardwood is priced by the rough thickness, before planing.
How much extra lumber should I buy?
Plan on 15 to 20 percent over your cut list for rough hardwood, and around 10 percent for dimensional lumber. Knots, checks, snipe and cutting mistakes eat more wood than most people expect.
Is a board foot the same as a linear foot?
No. A linear foot only measures length. A board foot measures volume, so a 1x12 and a 2x6 both have 1 board foot per linear foot, while a 1x4 has only 1/3 board foot per linear foot.
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