Board Foot Calculator

How this is calculated

A board foot is a volume: 144 cubic inches, or a piece 1 inch thick, 12 inches wide and 1 foot long. The formula is thickness in inches x width in inches x length in FEET, divided by 12. The 12 is what converts the mixed units - two measurements in inches and one in feet. Hardwood thickness is sold in quarter-inch increments and spoken as quarters: 4/4 is one inch, 5/4 is an inch and a quarter, 6/4 is an inch and a half, 8/4 is two inches. It is read aloud as 'four-quarter', not 'four over four'. ⚠️ THE RULE THAT SURPRISES PEOPLE: board feet are always calculated on the ROUGH thickness, never on the surfaced thickness you take home. A 4/4 board surfaced on two sides comes out around 13/16 to 7/8 of an inch - but it is still tallied and priced as 4/4, a full inch. That is not a trick. Surfacing is a service performed on wood you have already bought, and the material planed off was yours. You are paying for the rough board and paying for it to be flattened. It is why a yard will often sell you rough stock more cheaply per board foot, and why buying rough is worth it if you own a planer. It also means your project needs planning around the FINISHED thickness. If a design needs three quarters of an inch of finished material, 4/4 works with a little to spare. If it needs a full inch finished, you need 5/4, and buying 4/4 for it is a mistake no amount of careful planing will fix. Width is measured at the narrowest point on a board with uneven edges, and hardwood is very often sold in random widths and lengths rather than dimensioned stock - so measure each board rather than assuming. This calculates volume only. It does not allow for waste, and hardwood waste is substantial: expect to buy noticeably more than your finished parts add up to, because of defects, snipe, checking at the ends, and the fact that grain and colour matching means rejecting perfectly sound wood.

Common questions

What is a board foot?

A volume, not a length: 144 cubic inches. A piece 1 inch thick, 12 inches wide and 1 foot long is exactly one board foot, and so is any other shape with the same volume - 2 inches by 6 inches by a foot is also one. That is why the same board foot count can arrive as very different-looking piles of wood, and why linear feet and board feet are not interchangeable.

What does 4/4 mean?

Four quarters of an inch, so one inch. Hardwood is sold in quarter-inch increments and spoken as quarters - 4/4 is 'four-quarter', 5/4 is an inch and a quarter, 6/4 an inch and a half, 8/4 two inches. Softwood construction lumber uses the nominal 2x4 convention instead, which is a different naming system entirely and also does not match the board you get.

Why am I charged for a full inch when my board is 13/16?

Because board feet are tallied on the ROUGH thickness, and surfacing is a service rather than a discount. The wood planed off was already yours - you paid for the rough board, then paid to have it flattened and made parallel. This is standard across the hardwood trade rather than one yard being sharp, and it is why rough stock is often cheaper per board foot: you are declining the service, not getting less wood.

So what thickness should I buy?

Work backwards from your FINISHED thickness. A 4/4 board surfaces to roughly 13/16 to 7/8, so it comfortably yields three quarters of an inch finished. If your design needs a full inch of finished material, you need 5/4 - buying 4/4 and hoping is a mistake no amount of careful planing will fix, because the material simply is not there.

How much extra should I buy?

More than your parts list, and usually by a lot. Hardwood waste comes from defects, checking at the board ends, snipe, and the plain fact that grain and colour matching means rejecting perfectly sound wood that does not suit the piece. Rough-sawn random-width stock also has to be ripped square before it is usable. This calculator gives volume only and adds nothing for any of that.

Is a board foot the same as a linear foot?

No, and confusing them is expensive. A linear foot is just length - it says nothing about how thick or wide the board is. A board foot is a volume. Eight linear feet of 4/4 by 6 inch stock is 4 board feet; eight linear feet of 8/4 by 12 inch is 16. The calculator shows both because linear feet is what you have to fit in the car.

Take it further with AI

Copy this into ChatGPT or Claude with your own numbers filled in. It hands over the figures this calculator worked out, so the answer is built on real arithmetic instead of a guess.

I used the Board Foot Calculator at https://www.bfcbrilliance.com/tools/board-foot-calculator.

What I entered:
- Thickness (quarters): ___
- Width (in): ___
- Length (ft): ___
- How many boards (boards): ___
- Price per board foot ($): ___

What it calculated:
- Total board feet: ___
- Board feet per board: ___
- Total cost: ___
- Cost per board: ___
- Total linear feet: ___

Use those figures as given — they are already worked out, so please don't recalculate or estimate your own. Help me turn them into a plan: what to buy or do, in what order, roughly what it should cost, and the mistakes people most often make with this job.

Where the job touches structure, gas, or electrics, tell me to check local building code and whether a permit or a licensed trade is required.

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