Board Foot Calculator

A board foot is a unit of volume used to measure lumber. One board foot equals a piece of wood that is 1 inch thick, 12 inches wide, and 12 inches long. Put another way, it's 144 cubic inches of wood.

The reason the lumber industry uses board feet instead of simple linear feet is that wood comes in wildly different thicknesses and widths. A 2x4 and a 2x12 are both 8 feet long, but they contain very different amounts of wood. Board feet account for all three dimensions at once, giving you a true measure of volume rather than just length.

It's worth knowing that board feet measure nominal dimensions, meaning the size of the board before it's dried and planed at the mill. A standard 2x4 is actually 1.5 inches by 3.5 inches in real life, but for board foot calculations, you use the nominal 2x4 values. Sawyers and lumber dealers have worked this way for generations, so it's the convention you'll run into everywhere.

Calculating board feet comes down to three measurements: thickness (in inches), width (in inches), and length (in feet or inches). Once you have those three numbers, you multiply them together and divide by 12 if your length is in feet, or divide by 144 if all three measurements are in inches.

The trickiest part for beginners is keeping units straight. Most people measure length in feet and thickness and width in inches, so the divide-by-12 version of the formula is the most common. If you ever mix up your units, your answer will be way off, so double-check before you calculate.

For a quick mental check: a standard 1x12 board that's 1 foot long is exactly 1 board foot. That's the anchor point. Anything thicker, wider, or longer adds proportionally to that base number.

The formula looks like this:

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

If you prefer to work entirely in inches, divide by 144 instead:

Board Feet = (Thickness in inches × Width in inches × Length in inches) ÷ 144

Both formulas give you the same result. Use whichever one matches how you measured.

Here's a quick example. Say you have a board that's 2 inches thick, 6 inches wide, and 8 feet long. Plug those numbers in: 2 × 6 × 8 = 96, then 96 ÷ 12 = 8 board feet. Simple as that.

For larger orders, you multiply the board feet per piece by the number of pieces you need. If you need 10 of those 2x6x8 boards, you're looking at 80 board feet total. That total is what you'll use when pricing lumber at a per-board-foot rate.

Knowing the board foot value of standard lumber sizes ahead of time speeds up your estimating. The table below shows nominal dimensions and the board feet per linear foot for the most common sizes you'll find at any lumberyard.

To find the total board feet for any of these sizes, just multiply the value in the right column by the length of your board in feet. A 2x6 that's 12 feet long contains 12 board feet. A 1x4 at 10 feet gives you 3.33 board feet. These per-linear-foot values are handy to memorize or keep on a reference sheet when you're estimating at the lumberyard.

Once you know how many board feet you need, figuring out cost is straightforward. Most hardwood dealers and sawmills price lumber by the board foot, so you just multiply your total board feet by the price per board foot.

Total Cost = Board Feet × Price per Board Foot

Say you need 50 board feet of walnut and it's priced at $12 per board foot. That's $600 before any taxes or delivery fees. Pretty simple math, but it's easy to underestimate how fast board feet add up on a larger project.

A few things to keep in mind when budgeting:

• Add a waste factor. Most woodworkers add 10 to 20 percent extra to account for defects, cutoffs, and mistakes. For rough-sawn or figured wood, some go as high as 25 percent.
• Hardwoods vs. softwoods. Softwood lumber at a big-box store is usually priced by the linear foot or by the piece. Hardwoods from a specialty dealer are almost always priced by the board foot.
• Rough vs. surfaced. Rough-sawn lumber is typically cheaper per board foot than S4S (surfaced on four sides) lumber, but you'll lose some thickness during planing.

Getting accurate board foot counts before you shop helps you avoid buying too little and making a second trip, or buying too much and blowing your budget.

People sometimes confuse board feet with cubic feet, and it's an easy mistake to make since both measure volume. The difference is scale and how each unit is used in practice.

One cubic foot equals exactly 12 board feet. So if you're ever converting between the two, just multiply cubic feet by 12 to get board feet, or divide board feet by 12 to get cubic feet.

In everyday woodworking, you'll almost never use cubic feet. Board feet are the language of the lumber trade. Cubic feet come up more often when you're dealing with whole logs, bulk firewood, or estimating material weights for shipping. Stick with board feet for anything involving dimensional lumber and you'll be speaking the right language.

Working through a few examples is the fastest way to get comfortable with this. Here are three common scenarios.

Example 1: Single Board
You have a hardwood plank that's 1.5 inches thick, 8 inches wide, and 10 feet long.
1.5 × 8 × 10 = 120
120 ÷ 12 = 10 board feet

Example 2: Multiple Boards, Same Size
You need 6 boards, each 2 inches thick, 6 inches wide, and 8 feet long.
First, one board: 2 × 6 × 8 = 96 ÷ 12 = 8 board feet
Then multiply by quantity: 8 × 6 = 48 board feet total

Example 3: Mixed Sizes
Your project calls for three different board sizes. Calculate each group separately, then add them up.

1. Four 1x6x12 boards: (1 × 6 × 12 ÷ 12) × 4 = 6 × 4 = 24 board feet
2. Two 2x8x10 boards: (2 × 8 × 10 ÷ 12) × 2 = 13.33 × 2 = 26.67 board feet
3. One 4x4x8 post: 4 × 4 × 8 ÷ 12 = 10.67 board feet

Total: 24 + 26.67 + 10.67 = 61.33 board feet

Adding up groups like this is exactly how you'd build a cut list for a furniture project or a framing estimate. Do each size separately, then total everything at the end.

Board feet show up constantly once you start working with wood. Here's where you'll encounter them most often.

• Furniture building. Cabinet makers and furniture builders use board feet to price out materials before cutting anything. A dining table might require 30 to 50 board feet of hardwood depending on the design and species.
• Hardwood purchasing. Unlike the big-box stores that sell pre-cut softwood by the piece, hardwood dealers sell lumber by the board foot. You'll need to calculate your needs before walking in.
• Sawmill orders. If you're buying directly from a sawmill, whether for rough-sawn slabs or custom-cut dimensional lumber, everything is quoted in board feet.
• Flooring estimates. Wood flooring is sometimes sold by the square foot, but when ordering from a mill or calculating raw material needs, board feet come into play.
• Timber framing. Large-scale timber frame construction relies on board feet to estimate material volumes for beams, posts, and rafters.
• Log scaling. Foresters and loggers use board feet to estimate the usable lumber yield from a standing tree or a felled log.

Getting fluent with board foot math pays off at every stage of a project. You'll buy smarter, waste less material, and price your work more accurately. Once you've run the numbers a few times, it becomes second nature.