Free board foot calculator
A board foot is the standard unit hardwood lumber is sold by — a piece one inch thick, twelve inches wide and twelve inches long, or 144 cubic inches of wood. This calculator turns your board's thickness, width and length into board feet, multiplies by how many boards you need, adds a hardwood waste margin, and — with a price per board foot — totals the lumber cost, updated live, as you type.
On this page15 sections
| Line | Board feet | Est. cost |
|---|---|---|
| Lumber (no waste) | 40.00 BF | $240.00 |
| Order with 15% waste | 46.00 BF | $276.00 |
Cost = board feet × $6.00/BF. Hardwood is priced at the rough nominal size; confirm the price per board foot and board sizes with your supplier.
Board feet use nominal sizes; prices vary by species and supplier. How accurate is this?
Results are estimates. Consult a professional.
How the board foot calculator works
Hardwood lumber is priced by volume, not by the square foot or the linear foot, and the unit that volume is measured in is the board foot. One board foot is a piece of wood one inch thick, twelve inches wide and twelve inches long — 144 cubic inches of wood. The calculator takes the thickness, width and length of your boards, works out the board feet in a single board, multiplies by how many boards you need, and — if you enter a price per board foot — gives you the total material cost.
Why divide by 144
Multiply thickness, width and length all in inches and you get cubic inches. Because a board foot is defined as 144 cubic inches, dividing by 144 converts that raw cubic-inch figure into board feet. When the length is already in feet, the conversion folds in and you divide by 12 instead — the answer is identical.
What goes into a board foot estimate
A board foot estimate is built from four pieces: the three dimensions of a board, and how many of those boards you are buying. Get the dimensions in the right units and the volume is exact; the only judgement call is the waste margin you add on top.
Thickness — measured in quarters
Rough hardwood thickness is quoted in quarters of an inch: 4/4 is one inch, 5/4 is one and a quarter, 6/4 is one and a half, 8/4 is two inches. For board-foot math you use that rough nominal thickness, not the thinner dimension you end up with after planing — that is the convention the sawmill prices to.
Width and length — the rest of the volume
Width is measured in inches and length in feet (or inches). Rough boards come in random widths and lengths, so for an exact order you tally each board on its own. For planning, an average width and a standard length get you close.
Quantity and waste — turning one board into an order
The per-board figure is multiplied by how many boards you need, and then a waste margin is added because no project uses every inch of rough lumber. Defect cuts, grain matching, saw kerf and end trimming all eat into the pile.
A worked example using the board foot calculator
Maria is building a set of shelves and needs ten boards of poplar, each 1 inch thick, 6 inches wide and 8 feet long. Her supplier quotes $6.00 per board foot. She wants the total board feet, the material cost, and how much extra to buy for a hardwood project.
Step 1 — Board feet in a single board
Length is in feet, so divide by 12: 1 × 6 × 8 ÷ 12 = 4 board feet per board.
Step 2 — Multiply by the quantity
Ten boards: 4 × 10 = 40 board feet. That is the headline volume of lumber, before any waste.
Step 3 — Material cost
At $6.00 per board foot, 40 × $6.00 = $240 for the bare 40 board feet.
Step 4 — Add the hardwood waste margin
Hardwood projects lose wood to defects and matching, so add 15%: 40 × 1.15 = 46 board feet, which at $6.00 is $276. Maria orders 46 board feet so she is not caught short mid-build.
Board feet for common board sizes
If you just want a quick figure before you tally a stack, this table gives the board feet in a single board at common nominal sizes and lengths. Multiply by how many boards you need, then add a waste margin.
| Board (nominal) | Length | Board feet (each) |
|---|---|---|
| 1 in × 4 in | 8 ft | 2.67 |
| 1 in × 6 in | 8 ft | 4.00 |
| 1 in × 8 in | 8 ft | 5.33 |
| 1 in × 12 in | 8 ft | 8.00 |
| 2 in × 4 in | 8 ft | 5.33 |
| 2 in × 6 in | 8 ft | 8.00 |
| 2 in × 8 in | 10 ft | 13.33 |
| 5/4 in × 6 in | 8 ft | 5.00 |
Each figure is thickness(in) × width(in) × length(ft) ÷ 12, using nominal dimensions. 4/4 = 1 in, 5/4 = 1.25 in, 8/4 = 2 in.
When to use this board foot calculator
Reach for it whenever lumber is priced or quoted by the board foot — which is almost always the case for rough and hardwood stock, even though softwood at the home center is often sold by the piece.
- Buying hardwood — oak, walnut, maple, cherry and poplar are sold by the board foot at the rough size.
- Pricing a project — convert a cut list into total board feet, then multiply by the price per board foot for a material budget.
- Comparing suppliers — a price per board foot lets you compare two quotes on different board sizes apples-to-apples.
- Estimating a furniture build — tally the boards in a table, cabinet or shelf and add the hardwood waste margin before you order.
Waste factor: how much extra lumber to buy
Order the exact calculated board feet and you will run short. Rough hardwood arrives with knots, splits, sapwood and bow that you cut around; boards have to be trimmed to length; every cut loses a saw kerf; and on a fine piece you reject good wood simply because the grain does not match. A margin covers all of it.
The 15–30% rule for hardwood
Hardwood projects typically need 15–30% extra. A clean utility build off straight, clear boards can sit near 15%; furniture that demands grain and color matching, or stock with lots of defects, pushes toward 30%. The calculator defaults to 15% and lets you raise it. Framing lumber, which is more uniform, usually needs only 10–15%.
Why running short is worse than running over
Leftover lumber is money tied up, but running out mid-build is worse: a second order from a different batch can arrive a shade off in color or grain, and on a visible panel that mismatch shows forever. The margin exists so the boards you finish with all came from the same pile.
Board foot definitions
Board foot calculator FAQ
Is a board foot the same as a square foot?
No. A square foot measures area — length times width — and ignores thickness. A board foot measures volume and includes thickness. A 1-inch-thick board that covers one square foot is one board foot; a 2-inch-thick board over the same square foot is two board feet.
Do I use nominal or planed dimensions?
Use the nominal (rough) dimensions — a 1-inch board, an 8-foot length — because that is the size the sawmill prices and sells. The planed board is smaller, but you are paying for the wood that was milled off to get there.
How do I turn board feet into a cost?
Multiply the total board feet by the price per board foot your supplier quotes. Forty board feet at $6.00 per board foot is $240. Enter the price in the calculator and it does this for you, and also shows the cost once the waste margin is added.
A supplier quoted a price "per foot" — is that per linear foot or per board foot?
Always ask, because the two are not the same and the gap can be large. A price per linear foot ignores width and thickness, so the same dollar figure buys far less wood on a wide 8/4 board than the per-board-foot price implies. To convert a linear-foot price to a board-foot price, use $/BF = $/LF × 12 ÷ (thickness × width), with thickness and width in inches. A "$3 per foot" quote on a 1 in × 6 in board is $3 × 12 ÷ (1 × 6) = $6 per board foot.
Sources and references
The board-foot definition and formula are industry standards, sourced from woodworking and lumber references:
- Woodworkers Source — Board Foot Calculator & Definition: the T × W × L ÷ 144 formula (÷ 12 when length is in feet) and the 144-cubic-inch definition of a board foot.
- Board foot — Wikipedia: 1 BF = 144 cubic inches; nominal-vs-actual sizing and the FBM abbreviation.
- Inch Calculator — Board Footage Calculator: worked board-foot examples and quarter-inch (4/4, 5/4, 8/4) thickness convention.
- Omni Calculator — Board Foot Calculator: the length(ft) × width(in) × thickness(in) ÷ 12 formula, price-per-board-foot costing, and the waste-allowance step for ordering.
How accurate is this board foot calculator?
The board-foot math is exact. Thickness times width times length, divided by 144 (or by 12 when length is in feet), is the precise board-foot volume, and multiplying by quantity and price gives an exact total at the price you enter. If your dimensions are right, the board feet are right to the decimal.
The waste margin and the final order quantity are estimates, on purpose. Real hardwood loss depends on the species, the grade, how defect-free the boards are and how much grain matching the piece demands. The 15–30% range is guidance, not a guarantee, and prices move with species, grade, region and the day. So treat the with-waste figure and the cost as planning numbers, and confirm the price per board foot and board sizes with your supplier. When in doubt, order to the high side — a small overage is far cheaper than a mid-build shortage from a mismatched batch.
Frequently asked questions about the free board foot calculator
About this board foot calculator
This board foot calculator runs entirely in your browser — nothing you type is sent to a server. It uses the standard sawmill formula (thickness × width × length ÷ 144, or ÷ 12 when length is in feet), multiplies by your board count, and applies a hardwood waste factor and an optional price per board foot, recomputing instantly as you adjust any input.
It is one of our construction calculators. For pouring footings, slabs or pads for your build, see the concrete calculator, or browse the full calculator directory.