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Board Foot Calculator

A board foot is nominal volume. A third of it is not there

A board foot is nominal thickness times nominal width times length, divided by twelve. It is not the volume of wood. A 2x4 measures an inch and a half by three and a half, so 34% of every board foot on the invoice is not there. That is the convention rather than a trick, and this shows both numbers at once.

Board feet and actual volume

ft
no.
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Board feet use the nominal size, as the trade bills them. Actual volume uses the dressed size, which is the wood you get.

Specification summary

Generated from on . Reopen that address to reproduce these figures exactly.

Entered

Result

what you are billed forwhat you receive
Nominal against actual, at the same scale

Why there is no lumber price on this page

Because no lumber price meets the bar this site sets. Every figure of money published here has to carry a named source, a byline and a publication date. For framing lumber, sheathing and deck boards the free figures carry none of those, and the ones that do are behind a trade subscription that cannot be quoted.

Lumber is also the worst possible candidate for a national average. It moves week to week, it moves differently by region, and delivery on a small order can be a fifth of the ticket. A number printed here in September would be wrong in November and wrong in most of the country on the day it was written.

What can be published honestly

The Producer Price Index, softwood lumber from the US Bureau of Labor Statistics, series WPU0811. It is free, dated, and revised on a published schedule. It stood at 300.614 in July 2026, +15.0% against July 2025.

Over the twelve months to July 2026 the series ran between 250.132 and 300.614, a swing of 20%. That is the useful part: it tells you that a quote you were given four months ago is not a quote any more, and it tells you roughly by how much.

US Bureau of Labor Statistics series WPU0811, Producer Price Index, softwood lumber, read 2026-09-07. An index is not a price. It tracks what producers charge at the mill, not what your yard charges you across the counter, and the gap between those two is itself regional. Use it for the direction of travel and the size of the move, never to set a figure.

What to do instead

Take the quantity list this page produces to two yards and ask them to price it. That is a real number for your job on the day you ask, which is the only kind that exists. The quantities are the part this site can get exactly right, and they are the part that decides whether the two quotes are comparable.

This site publishes no price of its own. Why, and what that means for these figures.

Worked example

One hundred 2x4s, 8 ft long, kiln dried.

  1. Each. 2 × 4 × 8 / 12 = 5.33 board feet, on the nominal size.
  2. Total. 533 bf, or 0.533 MBF, which is how lumber is traded.
  3. Actual wood. 1.5 × 3.5 in over 800 linear feet is 29.17 cu ft.
  4. The gap. A board foot is 1/12 cu ft, so 533 bf would be 44.4 cu ft if it were real. 34% of the billed volume is not there.
  5. Weight. 29.17 cu ft at 30 lb/cu ft is 875 lb, or 8.8 lb a stick.

The 34% is not the same on every size. It is 34% on a 2x4, 31% on a 2x6 and 30% on a 2x12, because the half inch lost off the width matters less as the board gets wider. A 4x4 is the best of the common sizes at 23%.

The formula

Two volumes, and only one of them is wood:

bf = tnom × wnom × L / 12    cu ft = tact × wact × 12L / 1728
t, w nominal
2 and 4 for a 2x4. What you are billed on
t, w actual
1.5 and 3.5. What arrives
L
length in feet
MBF
a thousand board feet, the unit lumber is actually traded in

One board foot is one twelfth of a cubic foot by definition, so the two figures would agree if lumber were sold at its nominal size. It is not, and the gap is widest on the smallest sections.

Why a 2x4 is not two by four

Lumber is sawn at the nominal size and then dried and dressed, and both take material off. What arrives has been planed on four sides to a standard finished dimension, and those dimensions are set by the American Softwood Lumber Standard PS 20.

The convention that survived is that the board is still named and billed at the size it was sawn at. That is why board feet use the nominal dimensions: the unit is a measure of the log's output, not of the timber in your hand.

The gap is not constant. A 2x4 loses 34% of its nominal area, a 2x6 loses 31% and a 2x12 loses 30%, because the half inch taken off the width is a smaller share of a wider board. A 4x4 does best of the common sizes at 23%. Anyone comparing prices per board foot across sizes is comparing slightly different things.

Rough sawn lumber is the exception worth knowing. It has not been dressed, so a rough 2x4 is close to a genuine two by four, and its board feet and its actual volume nearly agree. That is part of why rough stock is priced the way it is.

Weight, and why it moves so much

Wood weight is water weight. Kiln dried softwood at 19% moisture content runs roughly 28 to 32 lb per cubic foot. The same species green off the saw can be 45 to 50, and freshly pressure treated lumber can exceed 60 because the treatment is carried in water.

The practical consequences are load and shrinkage. A pallet of treated 2x6 delivered wet is substantially heavier than the same pallet six months later, and every one of those boards will shrink across its width as it dries. That is why treated deck boards are usually gapped tighter than dry ones: they are going to open up on their own.

If weight actually matters, for a lift or a load calculation, weigh a piece. The density options here are typical values and the spread between them is larger than any error you are likely to make elsewhere in the calculation.

MBF, and why lumber is quoted that way

Lumber is traded in thousands of board feet, written MBF, from the Roman numeral. A price of $600 per MBF is 60 cents a board foot, and futures, mill quotes and market reports all use MBF.

Retail is different: dimensional lumber is usually priced per piece, and converting back to a board foot price is the only way to compare a 2x4 against a 2x6 honestly.

A 2x4x8 is 5.33 bf. A 2x6x8 is 8 bf. If the 2x6 is less than 1.5 times the price of the 2x4, it is cheaper wood.

Where board feet are the wrong unit

Sheet goods are sold by the sheet and quoted per square foot, not per board foot. The sheathing calculator handles those.

Framing is easier to order in pieces than in board feet, because you are buying specific lengths. The wall framing calculator gives both, so you can order in pieces and check the invoice in board feet.

Hardwood is where board feet genuinely earn their place, because it is sold in random widths and lengths and quoted in quarters: 4/4 is one inch nominal, 8/4 is two. There the board foot is the only sensible unit.

Frequently asked questions

How do you calculate board feet?
Nominal thickness in inches times nominal width in inches times length in feet, divided by 12. A 2x4x8 is 2 times 4 times 8 over 12, which is 5.33 board feet.
Is a board foot the actual volume of wood?
No. It uses the nominal size, so on a 2x4, which actually measures 1 1/2 by 3 1/2 in, about 34% of the billed volume is not physically present. One board foot is one twelfth of a cubic foot by definition, and the two would only agree if lumber were sold at its sawn size.
Why is a 2x4 actually 1.5 by 3.5 inches?
It is sawn at two by four and then dried and dressed on four sides, which takes material off. The finished dimensions are set by the American Softwood Lumber Standard PS 20, and the convention is that the board keeps the name and the billing of the size it was sawn at.
How much does a 2x4 weigh?
An 8 ft kiln dried 2x4 is about 9 lb at 30 lb per cubic foot. Green it can be 14, and freshly pressure treated closer to 17, because the treatment is waterborne. Weight is water weight and it moves more than anything else in the calculation.
What is MBF?
A thousand board feet, from the Roman numeral M. It is the unit lumber is traded in: a price of $600 per MBF is 60 cents per board foot. Retail dimensional lumber is priced per piece instead, so converting back is the only honest way to compare sizes.
Is a 2x6 better value than a 2x4?
A 2x4x8 is 5.33 bf and a 2x6x8 is 8 bf, so a 2x6 is 1.5 times the wood. If it costs less than 1.5 times the price, it is cheaper per board foot. It also loses slightly less to dressing: 31% against 34%.
Do rough sawn boards measure their nominal size?
Close to it, yes. Rough sawn, or rough cut, stock has not been dressed, so a rough 2x4 is near a genuine two by four and its board feet and actual volume nearly agree. That is part of why it is priced differently.
How many board feet is a 4x4 post?
A 4x4 post 8 ft long is 4 times 4 times 8 over 12, which is 10.67 board feet. Dressed, it measures 3 1/2 by 3 1/2 in, so about 23% of the billed volume is not there, less than on a 2x4 because a square section loses proportionally less.
How many board feet is a 2x8?
A 2x8x8 is 10.67 board feet, the same as a 4x4x8. It dresses to 1 1/2 by 7 1/4 in, so about 32% of the billed volume is not physically present.
Is cedar or redwood lumber measured differently?
No. The board foot is a volume convention, so cedar, redwood and pine of the same nominal size and length have the same board feet. What changes between species is the price per board foot and the weight.
How many board feet are in a 2x10 or a 6x6?
A 2x10x8 is 2 times 10 times 8 over 12, which is 13.33 board feet, and it dresses to 1 1/2 by 9 1/4 in, so about 31% of the billed volume is not there. A 6x6 post 8 ft long is 24 board feet and dresses to 5 1/2 by 5 1/2 in, losing about 16%. Pressure treated at the 58 lb per cubic foot figure above, that 6x6 weighs about 97 lb. This page prints no lumber price for either.
How is cherry lumber measured and priced?
Cherry is a hardwood, so it is sold by the board foot in random widths and lengths and quoted in quarters, where 4/4 is one inch nominal. A 4/4 cherry board 6 in wide and 8 ft long is 1 times 6 times 8 over 12, which is 4 board feet. This page publishes no hardwood price, so multiply the board feet by what your supplier quotes per board foot.

Check these numbers yourself

How every figure here is verified: Sources & Method. Who builds this: , and the method is on About. Found something wrong? Tell us and it gets fixed or removed.

Figures on this page last checked against the source documents on 2026-09-08. Codes are amended locally; confirm against the edition your jurisdiction enforces.

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Board feet are a billing unit, not a volume. They use nominal dimensions and overstate the wood present by 23 to 34% depending on the size. Density figures are typical values only: moisture content moves weight by half again, so weigh a piece if the weight matters.