Board Foot Calculator

Board foot calculator for nominal lumber, measured boards, NHLA hardwood tallies, square-foot coverage and Doyle, Scribner or International log scale, with its cost and dry weight.

Board Foot Calculator Formula and Units

A board foot is 144 cubic inches of wood, the volume of a piece 12 in long, 12 in wide and 1 in thick. That makes it 1/12 of a cubic foot, so 12 board feet fill one cubic foot and about 424 board feet fill one cubic meter. Lumberyards, sawmills and hardwood dealers across the US price and tally wood in this unit, so every board foot calculator estimate starts here.

$$BF=\frac{T\times W\times L}{12}$$

T is thickness in inches, W is width in inches and L is length in feet. With all three sizes in inches, divide by 144 instead of 12. A board 1.25 in thick, 10 in wide and 8 ft long holds 8.33 BF, so five of those boards add up to 41.67 BF, and at $4.15 per board foot the order costs $172.92.

Mixed units cause most wrong answers worked by hand. Length in inches divided by 12 overstates the volume twelve times, so a 10 ft board at 2 in × 8 in comes out as 160 BF instead of the correct 13.33 BF. Keep length in feet whenever the divisor is 12, and switch to 144 only when every size is in inches. A board foot calculator estimate that comes out twelve times too high almost always has length in inches over 12.

Metric boards convert before the multiplication, at 25.4 mm per inch and 0.3048 m per foot. A 32 mm × 250 mm board 2.44 m long becomes 1.26 in × 9.84 in × 8.0 ft, which is 8.27 BF. Convert each size before multiplying, as rounding the product instead can drift by a tenth of a board foot on long boards.

To measure a board foot on a real board, read thickness at the thinnest clean spot and width at mid-length. On a tapered or live edge, measure both ends and average them, the method sawyers on the Forestry Forum use for wane boards. Small misreads add up fast: a width off by 1/4 in on a 1 in × 12 ft board shifts the count by 0.25 BF per board.

Nominal 2x4, 2x6 and 2x10 Board Feet

Lumberyards bill dimension lumber on nominal size, but dry softwood lumber under the American Softwood Lumber Standard (PS 20) is planed smaller. A 2x4 dresses to 1.5 × 3.5 in, so an 8 ft stud is billed as 5.33 BF and carries only 3.5 BF of wood. Any board foot calculator for lumber needs both numbers, since the billed figure sets the price and the real figure sets the weight.

The planing loss is close to a fixed half inch on each face size, so small stock loses the most. A 2x2 keeps only 56% of its billed board feet, while a 6x6 keeps 84%. Widths of 8 in and up lose 3/4 in instead, which is why a 2x10 is 9.25 in wide and a 2x12 is 11.25 in. A board foot calculator total built on measured 1.5 × 3.5 in sizes will therefore read 34% below a lumberyard bill for the same 2x4s.

A 2x4 holds 0.667 BF per linear foot on nominal size, which gives 4 BF at 6 ft, 9.33 BF at 14 ft and 13.33 BF at 20 ft. Each extra 2 ft of stud adds 1.33 BF. For a full wall or floor take-off, the Framing Calculator counts studs and plates and the Floor Joist Calculator sets joist count and spacing, so the board foot calculator total comes from a real piece list.

Hardwood Quarter Sizes and the NHLA Tally

Hardwood is sold by rough thickness in quarters of an inch, where 4/4 is 1 in, 5/4 is 1.25 in and 8/4 is 2 in. The board foot formula for hardwoods is still T × W × L ÷ 12, but dealers working to NHLA rules round each board before they multiply, which is why a board foot calculator count on exact sizes and a dealer tally rarely match to the board foot. A hardwood board foot estimate that skips those rounding steps can miss the dealer count by 10% or more on a single board.

Under the NHLA grading rules, surface measure (SM) is width in inches times length in feet, divided by 12 and rounded to the nearest whole number. Widths round to the nearest inch, fractions of a foot are dropped, and SM times the nominal thickness class gives the billed board feet. Stock under 1 in counts as 4/4, and kiln-dried rough lumber may run 1/16 in scant (1/8 in from 2 in up) and still bill in its class.

$$B{F}_{tally}=SM\times T_{quarter}$$

The American Hardwood Export Council grading guide adds two details buyers often miss. Widths and surface measures falling exactly on a half are rounded up and down on alternate boards, so two 7-1/2 in boards tally as one 8 in and one 7 in board. Lumber sold on a green tally yields about 7% fewer board feet once it has been kiln dried, so a green-tally price needs that loss built in when you compare two dealers.

The rounding cuts both ways. Rough 4/4 is commonly sawn about 1/8 in heavy and still sold as 4/4, so a dealer tally often bills less wood than you carry out, while a kiln-dried 8/4 board down to 1-7/8 in still bills as a full 2 in. Thin planed stock goes the other way, because a 3/4 in board is paid for as a full inch. Working the board foot calculator count on exact sizes and again on the tally tells you which side of that gap a load falls on.

Board feet per linear foot by quarter thickness and width make quick work of a stack of random-length boards. Group the boards by width, add up the length of each group, and multiply by the value in the table, which turns a whole pile into a board foot calculator total in a few lines instead of one board at a time.

Surfaced hardwood loses thickness too, yet it is still billed on the rough quarter. The same AHEC guide puts finished thickness at nominal minus 3/16 in for stock up to 1-1/2 in, so S2S 4/4 is 13/16 in and S2S 6/4 is 1-5/16 in. A project that needs a true 1 in finished part has to start from 5/4 rough stock and pay for 25% more board feet.

Linear Foot vs Board Foot Pricing

A linear foot measures length only, while a board foot adds thickness and width. One linear foot of a T × W board holds T × W ÷ 12 board feet, and that ratio converts any per-foot shelf price into a board-foot rate. A price per board foot calculator runs on exactly this ratio, so the table below can stand in for one at the lumberyard counter.

$$P_{BF}=\frac{12\times P_{LF}}{T\times W}$$

P_LF is the price per linear foot and T × W is the billed size in inches. Price per MBF, the rate mills and wholesalers quote, is simply the price per board foot times 1,000, so $4.15 per BF equals $4,150 per MBF. The sample shelf prices below show how far apart two per-foot prices can be once converted.

The cost of a board is its board feet times the price per board foot. A 4/4 walnut board 6 in wide and 8 ft long is 4 BF, so at $12.50 per BF it costs $50. A mixed order works the same way: price each board size on its own line, then add the lines together for the total.

Waste belongs in the board foot calculator count before pricing, not on the bill afterward. Five boards at 8.33 BF with 15% waste become 47.92 BF to buy, which rounds up to six whole boards. At $4.15 per BF, that order costs $172.92 before waste and $198.85 after it, a gap worth knowing before the lumberyard trip.

Square Feet to Board Feet for Floors, Siding and Foam

One square foot of material 1 in thick is one board foot, so board feet equal area in square feet times thickness in inches. That makes 320 sq ft at 1 in exactly 320 BF, 240 BF at 3/4 in and 640 BF at 2 in. Thickness is the only number a board foot calculator to square feet conversion needs beyond the area itself.

$$BF=A\times T$$

A is the area in square feet and T is the thickness or depth in inches. Reversing the formula gives coverage, so 200 BF covers 200 sq ft at 1 in thick but only 100 sq ft at 2 in. The table runs both directions for common board and foam thicknesses.

Spray foam and rigid foam insulation are rated in board feet on the same definition, so board foot insulation is simply area times depth. A 500 sq ft wall sprayed 3 in deep needs 1,500 BF of foam before any overspray or yield loss. A board foot calculator for spray foam is the same area-times-depth math as for lumber.

The square footage of a single board is its face area, width in inches times length in feet divided by 12. A 10 in × 8 ft board has 6.67 sq ft of face, the same number NHLA calls surface measure. Sheet goods are counted in sheets instead, which the Plywood Calculator handles, and vertical siding is counted by piece in the Board and Batten Calculator.

Flooring and decking need face width, not billed width, for coverage. Boards with a 5.5 in face covering 320 sq ft take 698 linear feet before waste, so planning on a 6 in nominal width would leave the order about 58 LF short of the floor.

Log Board Feet by Doyle, Scribner and International Rules

Log scale estimates the lumber a sawmill can cut from a log, not its solid volume, and a log board foot calculator result depends on which of three log rules the buyer uses. Measure the small end inside the bark twice at right angles and average the readings. Purdue Extension FNR-191 also drops hardwood log lengths to the next lower foot.

$$B{F}_{Doyle}=(D-4{)}^2\times \frac{L}{16}$$

$$B{F}_{Scribner}=(0.79D^2-2D-4)\times \frac{L}{16}$$

$$B{F}_{Intl}=0.905\times \sum (0.22D_i^2-0.71D_i)$$

D is small-end diameter in inches and L is log length in feet. The International 1/4-inch rule sums each 4 ft section, with D_i growing 1/2 in per section to allow for taper, and the 0.905 factor adjusts the 1/8 in kerf base to a 1/4 in saw kerf. All values in the table are for a 16 ft log.

Doyle subtracts 4 in from the diameter for slabs, which badly underscales small logs: an 8 in log scores 16 BF against 39 BF on the International rule. The rules meet near 28 in, and Doyle runs over on anything larger. A load of 12 in logs sold on Doyle comes out about a third short of International, so ask which rule the buyer uses before agreeing on a price per MBF.

Shorter logs follow the same pattern, with a 16 in × 12 ft log at 108 BF Doyle, 125 BF Scribner and 131 BF International. Published tables round their numbers, so formula results differ from a printed table by a few board feet. Purdue notes that Scribner Decimal C tables round to the nearest 10 BF and International tables to the nearest 5 BF.

A board foot calculator for standing timber uses these same rules once the merchantable log length and top diameter have been judged from the tree. Before hauling cut logs, the Log Weight Calculator turns the same diameter and length into green weight for the truck or trailer.

Weight per Board Foot by Species

Weight per board foot is wood density divided by 12, so any board foot calculator total converts to pounds with one multiplication. Kiln-dried density at 12% moisture comes from specific gravity, using the relationship in USDA Forest Products Laboratory report GTR-76 and the 12% specific gravity values published in the USDA Wood Handbook.

$${\rho }_{12}=SG\times 62.4\times 1.12$$

SG is specific gravity at 12% moisture, 62.4 lb/ft³ is the density of water and 1.12 adds the 12% water held in dry wood. Red oak at SG 0.63 works out to 44.0 lb/ft³, which is 3.67 lb per board foot and 367 lb per 100 BF. Multiply the order's board feet by the weight per BF below to get the load of a whole order.

A board foot of oak weighs about 3.7 lb for red oak and 4.0 lb for white oak when kiln dried. Weight follows the real wood, not the billed size, so an 8 ft southern pine 2x4 holds 3.5 BF of wood and weighs about 10.4 lb, not the 15.8 lb its nominal 5.33 BF would suggest. Framing lumber weight always comes from dressed sizes for that reason.

These figures assume 12% moisture, the usual state of kiln-dried lumber stored indoors. Wet wood weighs more for two reasons: the water itself, and the extra volume wood gains as it swells up to about 30% moisture. The Wood Handbook adjusts specific gravity for both effects.

$$G_M=\frac{G_b}{1-0.265\cdot a\cdot G_b},a=\frac{30-M}{30}$$

G_b is basic specific gravity (oven-dry weight over green volume), M is moisture content in percent, and a drops to 0 above 30% moisture. Density is then G_M × 62.4 × (1 + M/100), which is how red oak climbs from 44.0 lb/ft³ kiln dried to about 64 lb/ft³ green at 80%.

At 80% moisture, a 500 BF pile of fresh-sawn red oak weighs about 2,680 lb, against 1,835 lb once kiln dried. Use the wood's real moisture for any board foot calculator weight headed for a truck, trailer or loft floor, since a kiln-dried figure understates that green load by about a third. The Lumber Weight Calculator works from board size and species, and the Lumber Calculator turns a project into piece counts before you total the board feet.

Common Board Foot Answers by Size and Species

Lumberyards bill a 2x4 as a full 2 × 4 in even though it measures 1.5 × 3.5 in, so each lumber size below gives the billed board feet first and the real planed wood second. The billed figure sets what you pay, and the planed figure sets the weight and true volume.

What is a board foot?

A board foot is a unit of wood volume equal to a piece 1 ft long, 1 ft wide and 1 in thick. It holds 144 cubic inches, which is 1/12 of a cubic foot or about 0.00236 cubic meters. US lumberyards, sawmills and hardwood dealers price lumber per board foot or per thousand board feet (MBF), so any board foot calculator estimate comes back to this unit.

How do you calculate board feet?

Multiply thickness in inches by width in inches by length in feet, then divide by 12. A 2 in × 6 in × 12 ft board is 2 × 6 × 12 ÷ 12 = 12 BF. With every size in inches, divide by 144 instead, so the same board as 2 × 6 × 144 in also gives 12 BF. Multiply by the number of pieces for the order total. The same rule sits behind every board foot calculator and every hand tally at the lumberyard.

Board footage for a mixed stack works the same way, one size at a time. Ten 1x6x8 boards (40 BF), six 2x4x10 studs (40 BF) and four 2x10x12 joists (80 BF) add up to 160 BF of board footage for the order.

How do I calculate the cost of a board?

Multiply the board feet in the board by the price per board foot. A 1 in × 8 in × 10 ft cherry board holds 6.67 BF, so at $9.00 per BF it costs $60.00. Board feet and price per BF are the only two numbers a board foot calculator cost estimate needs. For a price per linear foot, divide by the board feet in one foot of that board: $3.00 per LF on 1 × 6 stock is $6.00 per BF, because each foot of a 1 × 6 holds 0.5 BF.

How do you measure a board foot?

Measure thickness and width in inches and length in feet, then apply the board foot formula. On rough hardwood, read thickness at the thinnest clean spot and width at mid-length, and average both ends on a tapered board. Dealers following NHLA rules round width to the nearest inch, drop fractions of a foot from the length and round surface measure to a whole number before multiplying by the thickness class, so the measured size and the board foot calculator figure from a tally can differ.

How many board feet are in a 2x4?

A nominal 2x4 holds 0.667 BF per linear foot, so the total depends on its length. A 2x4x8 is 5.33 BF, a 2x4x10 is 6.67 BF, a 2x4x12 is 8 BF and a 2x4x16 is 10.67 BF. The planed wood, at 1.5 × 3.5 in, is only 66% of each billed figure.

How many board feet is a 2x4x8?

A 2x4x8 is 5.33 board feet on nominal size: 2 × 4 × 8 ÷ 12 = 5.33. The actual stud is 1.5 × 3.5 in, which is 3.5 BF of real wood. In kiln-dried southern yellow pine that works out to about 10.4 lb per stud, and twelve studs make 64 BF billed.

How many board feet are in a 2x4x10?

A 2x4x10 holds 6.67 board feet: 2 × 4 × 10 ÷ 12 = 6.67. The dressed 1.5 × 3.5 in stud carries 4.38 BF of real wood. Fifteen of them make 100 BF, a handy round number when a yard quotes framing by the MBF.

How many board feet are in 2x3x10?

A 2x3x10 holds 5 board feet: 2 × 3 × 10 ÷ 12 = 5. Dressed to 1.5 × 2.5 in, it carries 3.13 BF of wood, or 63% of the billed volume. Two-by-threes lose a larger share to planing than 2x4s because the same half inch comes off a narrower board.

How many board feet is a 2x2x8?

A 2x2x8 is 2.67 board feet: 2 × 2 × 8 ÷ 12 = 2.67. The dressed piece is 1.5 × 1.5 in, which is only 1.5 BF of wood, so 44% of what is billed is lost to planing. Small stock like this is often sold per piece or per linear foot, so convert the price to $/BF before comparing it with other stock.

How many board feet in a 2x2x12?

A 2x2x12 holds 4 board feet: 2 × 2 × 12 ÷ 12 = 4. The real 1.5 × 1.5 in piece is 2.25 BF of wood. Each 2x2 adds 0.333 BF per linear foot, so stretching from 8 ft to 12 ft adds 1.33 BF, and a bundle of 25 pieces at 12 ft comes to 100 BF.

How many board feet is a 2x6x10?

A 2x6x10 is 10 board feet: 2 × 6 × 10 ÷ 12 = 10. Dressed to 1.5 × 5.5 in, it holds 6.88 BF of wood. A nominal 2x6 holds exactly 1 BF per linear foot, so its length in feet equals its board feet, which makes 2x6 pricing per LF and per BF the same number.

How many sq ft is 1 board foot?

One board foot covers 1 sq ft at 1 in thick. At other thicknesses, coverage is 1 divided by the thickness in inches: 1.33 sq ft at 3/4 in, 0.67 sq ft at 1.5 in and 0.5 sq ft at 2 in. A board foot is volume, so it only converts to square feet once a thickness is fixed.

How much will 200 board feet cover?

Two hundred board feet cover 200 sq ft at 1 in thick, 266.7 sq ft at 3/4 in, 133.3 sq ft at 1.5 in and 100 sq ft at 2 in. That is gross coverage; tongue-and-groove and shiplap boards cover only their face width, and cutting waste comes on top.

How many board feet are there in 320 square feet?

An area of 320 sq ft holds 320 board feet at 1 in thick. At 3/4 in it is 240 BF, at 1.5 in it is 480 BF and at 2 in it is 640 BF. For spray foam, 320 sq ft at 3 in deep is 960 BF of foam before overspray.

How to find sq ft of a board?

Multiply the board's width in inches by its length in feet and divide by 12. A 6 in × 10 ft board has 5 sq ft of face, and a 10 in × 8 ft board has 6.67 sq ft. For a 1 in board this face area equals its board feet, and for thicker stock the board feet are the face area times the thickness.

What is the difference between a board foot and a linear foot?

A board foot measures volume and a linear foot measures length only. One linear foot of a 1 × 12 board holds 1 BF, while one linear foot of a 1 × 4 holds only 0.333 BF. That is why $1.00 per LF on 1 × 4 stock equals $3.00 per BF, three times the per-foot price, so convert both quotes to $/BF before any board foot calculator cost total on mixed stock.

How do you calculate the board feet in a log?

Measure the small-end diameter inside the bark in inches and the log length in feet, then apply a log rule. Doyle is (D - 4)² × L ÷ 16, so a 14 in × 16 ft log scales 100 BF. The same log scales 123 BF on Scribner and 136 BF on the International 1/4-inch rule. Ask the buyer which rule sets the price, since a log board foot calculator on the wrong rule can miss by a quarter.

How much does a board foot of oak weigh?

A board foot of kiln-dried red oak weighs about 3.67 lb, and white oak about 3.96 lb. Green from the sawmill at 80% moisture, the same board foot weighs about 5.36 lb in red oak and 5.74 lb in white oak. Those figures come from USDA Wood Handbook specific gravities of 0.63 and 0.68 at 12% moisture. A 100 BF order of white oak weighs close to 400 lb.

What is board foot insulation?

Board foot insulation is spray foam or rigid foam measured as 1 sq ft at 1 in thick, the same volume as a lumber board foot. Foam kits are rated in board feet, so a 600 BF kit sprayed 2 in deep covers 300 sq ft before yield losses. Filling a full 3.5 in stud cavity over the same 300 sq ft takes 1,050 BF, so depth drives a foam order more than area does.