Board Foot Calculator
Add every board to one running tally and get total board feet, cost, and how much to order with waste. Free, instant, and it saves your list in this browser.
| Qty | Thickness | Width | Length | Board feet | |
|---|---|---|---|---|---|
| 40 | |||||
| 21.33 |
Board feet use the formula thickness x width x length in inches, divided by 144. Lumber is normally figured at nominal size (a 2x4 counts as 2 by 4). Hardwood thickness is often given in quarters: 4/4 = 1", 5/4 = 1.25", 8/4 = 2". Your tally saves in this browser.
What a board foot is
A board foot is a unit of volume for lumber. One board foot equals 144 cubic inches, which is a piece one inch thick, twelve inches wide, and one foot long. It is not a measure of length or surface area, so you always need three numbers to find it: thickness, width, and length.
The formula is simple:
board feet = (thickness in x width in x length in) / 144
If your length is already in feet, you can skip a step:
board feet = (thickness in x width in x length ft) / 12
Why the tally matters
Nobody buys one board at a time. A real project is a cut list: a few 8 foot 1x6s, some 2x4s, a couple of wide boards for a top. Most calculators make you do one board, write down the answer, clear the form, and start over. This one keeps every board in a single table and adds them up as you go, so the number at the bottom is what you actually take to the lumberyard.
Add a price per board foot and it estimates the cost. Add a waste percentage and it pads the order for cutoffs, defects, and mistakes. Most woodworkers add 10 to 20 percent depending on how much ripping and crosscutting the design needs.
Nominal vs actual size
Lumber is figured at nominal size, not the size you measure with a tape. A construction 2x4 is really about 1.5 by 3.5 inches once it is planed, but it is bought and priced as a 2x4. Hardwood is a bit different: rough boards are close to their stated thickness and are sold in quarters, where 4/4 is one inch, 5/4 is one and a quarter, and 8/4 is two inches. Enter the nominal numbers and the tally matches what the yard charges you for.
Worked example
Say you need ten 1x6 boards at 8 feet and four 2x4s at 8 feet.
- Ten 1x6x8: 1 x 6 x 8 / 12 = 4 board feet each, so 40 board feet
- Four 2x4x8: 2 x 4 x 8 / 12 = 5.33 board feet each, so 21.33 board feet
- Total: 61.33 board feet
At 5 dollars per board foot with 15 percent waste, that is about 70.5 board feet to order and roughly 353 dollars of material. The calculator above does all of that as you type, and it saves your list in this browser so it is still there when you come back.
Frequently asked questions
- How do I calculate board feet?
- Multiply thickness in inches by width in inches by length in inches, then divide by 144. If the length is in feet, multiply thickness by width by length and divide by 12 instead. The calculator on this page does it for a whole list of boards at once.
- Is a board foot the same as a linear foot?
- No. A linear foot only measures length. A board foot measures volume, so it also depends on thickness and width. A 1x6 gives half a board foot per linear foot, while a 2x12 gives two board feet per linear foot.
- Do I use nominal or actual size?
- Use nominal size, the size the lumber is sold as. A 2x4 is figured as 2 by 4 even though it measures about 1.5 by 3.5 after planing, because that is how the lumberyard prices it.
- How much waste should I add?
- Most projects add 10 to 20 percent. Add more for short parts, a lot of ripping, rough or defect-prone stock, or if you are new to a cut and expect a few mistakes.
- Does this work for metric sizes?
- Yes. Switch the thickness and width unit to millimeters or centimeters and the length unit to meters. The result is still in board feet, the standard lumber unit in the US and Canada.