Lumber Calculator

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

A board foot measures volume. It is 1 in thick, 12 in wide, and 12 in long. 1 It counts thickness, width, and length. A linear foot (also called lineal foot) only measures length. A 10 ft 2×4 and a 10 ft 2×12 are both 10 linear feet, but the 2×12 holds about three times more wood.

Q: How many board feet are in a cubic meter?

One cubic meter holds about 424 board feet . One board foot equals about 0.00236 m³. To go from board feet to cubic meters, multiply by 0.00236. To go the other way, multiply cubic meters by 424.

Q: How long is a stud for an 8 foot wall?

Most 8 ft walls use a 92 5/8 in precut stud . Add the 1.5 in sole plate and two 1.5 in top plates, and the wall stands 97 1/8 in tall. That extra height leaves room for the floor and ceiling drywall, so a 96 in sheet still fits with no cutting.

Q: Is OSB or plywood better for sheathing?

OSB costs less and comes in bigger sheets. It is fine for walls and roofs that stay dry. Plywood dries faster after it gets wet, holds screws a bit better, and stays flatter. It is the safer pick for floors, roofs that may sit open in rain, and damp areas. Both meet code for sheathing at the same thickness.

Introduction

This lumber calculator works out how much wood you need and what it will cost. Type in a few numbers and you get board feet, piece counts, and totals. It works in both imperial (inches and feet) and metric (mm and meters) units.

The tool has four tabs:

Board Footage: Find board feet, MBFT, lineal feet, or piece count. Fill in any one box, and the rest fill in for you.
Pricing Converter: Turn a price per board foot into a price per piece, per MBFT, per lineal foot, or per cubic meter, so you can compare quotes side by side.
Framing Estimator: Count studs and plates for a wall or a whole room. Pick your lumber size, stud spacing, and stock length, then add doors and windows.
Sheet Goods: Find how many sheets of plywood or OSB cover your area.

Every tab adds a waste allowance, so you buy enough wood the first time. Add a price, and you get a cost estimate too. You also see the step-by-step math and a chart, so you know where each number comes from.

How to use our Lumber Calculator

Enter your board size, quantity, and price details, and the lumber calculator gives you board feet, MBFT, lineal feet, stud and plate counts, sheet counts, and your total material cost. Pick a tab for the job you need, then fill in the fields below.

Unit System: Choose Imperial or Metric. The calculator changes every input and answer to that system and converts what you already typed.

Waste Allowance (%): Type how much extra lumber you want for cuts and mistakes. Use 10% for simple work and 15% or more for angled or tricky cuts.

Price per Piece: Type what one board costs. This is optional, but it adds a cost estimate to each tab.

Board Footage Tab

Thickness: Enter the board's thickness. To match how lumber yards count board feet, enter the nominal size.¹ For the true volume of wood, enter the dressed size: a dry 2×4 is 1½ in (38 mm) thick.²

Width: Enter the board's width the same way. A dry 2×6 is 5½ in (140 mm) wide.²

Length (per piece): Enter how long one board is, in feet, inches, meters, or centimeters.

Pieces: Type how many boards you need. The other three quantity boxes fill in for you.

Board Feet / Volume: If you know the total board feet, cubic feet, or cubic meters instead, type it here and the piece count is worked backward.

MBFT: Type the total in thousand board feet if your supplier quotes that way.

Lineal Length: Type the total length of lumber in feet or meters if that is the number you have.

Pricing Converter Tab

Thickness, Width, and Length: These match the Board Footage tab. Change them here if you want to price a different board size.

Enter Your Known Price: Type the price your supplier gave you.

Price Unit: Pick the unit that price is based on, like per piece, per board foot, per MBFT, per lineal foot, per cubic meter, or per lineal meter. You then see the same price in every other unit.

Framing Estimator Tab

Nominal Lumber Size: Pick the board you are framing with, such as 2×4 or 2×6. The math uses the real dressed size.

Stock Length Purchased: Pick the board length you buy at the store.

Stud Spacing: Pick 16 in or 24 in on center (400 mm or 600 mm in metric).

Wall Length: Enter how long the wall is. In feet mode you can add extra inches in the small box.

Wall Width: Fill this in only if you are framing a full room. It adds all four walls as a perimeter.

Wall Height: Enter how tall the wall is, floor to top plate.

Top Plate: Choose single or double top plate. Double adds one more plate run.

Number of Doors: Enter how many doors are in the wall. Each door adds 4 studs.

Number of Windows: Enter how many windows are in the wall. Each window adds 4 studs.

Sheet Goods Tab

Area to Cover: Enter the surface size in square feet, square meters, or square yards.

Sheet Size: Pick the panel size you are buying, like 4 × 8 ft plywood or OSB.

Sheet Thickness: Pick the panel thickness. This is used for your order notes and cost line.

Price per Sheet: Type what one sheet costs to see your total sheet cost. This field is optional.

Understanding Lumber Measurements

Lumber is sold in a few different ways, and the units can be confusing. A lumber yard may quote a price per piece, per board foot, per thousand board feet, or per lineal foot. Knowing how these units connect helps you compare prices and order the right amount of wood for your project.

What Is a Board Foot?

A board foot is a way to measure the volume of wood. One board foot equals a piece 1 inch thick, 12 inches wide, and 12 inches long.¹ The formula is:

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

Board feet are used most often for hardwood and rough lumber. Softwood boards like 2×4s are often sold by the piece or by the lineal foot instead.

Nominal Size vs. Actual Size

A "2×4" is not really 2 inches by 4 inches. That is its nominal size, and the actual size is somewhat less.² A dry 2×4 is 1½ by 3½ inches (38 by 89 mm).² Board feet for lumber 1 inch or thicker are normally figured on the nominal thickness and width and the actual length¹, so a yard's board-foot count is higher than the actual volume of wood. Here are common dry sizes:

1×4 → ¾ × 3½ in (19 × 89 mm)²
2×4 → 1½ × 3½ in (38 × 89 mm)²
2×6 → 1½ × 5½ in (38 × 140 mm)²
2×8 → 1½ × 7¼ in (38 × 184 mm)²
2×10 → 1½ × 9¼ in (38 × 235 mm)²
2×12 → 1½ × 11¼ in (38 × 286 mm)²

Common Lumber Pricing Units

Per piece: the cost of one board at a set length.
BDFT: price for one board foot of wood.
MBFT: price for 1,000 board feet. Used for bulk orders.
Lineal foot (LF): price per foot of length, no matter the width.
Cubic meter (m³): the metric volume unit. One board foot equals about 0.00236 m³.

Wall Framing Basics

Wall studs are placed at a set spacing, measured on center (o.c.). That means from the middle of one stud to the middle of the next. The most common spacings are 16 inches and 24 inches (400 mm and 600 mm). A wall also needs plates: one sole plate on the bottom and one or two top plates on the top. Doors and windows need extra studs, such as king studs, jack studs, and cripples, so add about four extra studs for each opening.

Sheet Goods

Plywood, OSB, and drywall come in flat sheets. The standard sheet is 4 by 8 feet, which covers 32 square feet (about 2.97 m²). Longer 4×9 and 4×10 sheets are also sold. To find how many sheets you need, divide the area you are covering by the area of one sheet, then round up.

Why Add a Waste Allowance

You will never use every inch of every board. Cuts, mistakes, knots, and odd angles all waste wood. Most simple jobs use a 10% waste allowance. Use 15% or more for angled cuts, diagonal decking, or rooms with many corners. It is cheaper to buy a little extra than to make a second trip to the store.

Tips for Ordering Lumber

Pick a stock length that divides neatly into your cut size to cut down on off-cuts.
Check the actual dressed size on the tag before you do any math.
Convert every supplier quote to the same unit before comparing prices.
Round your final order up to whole pieces, since stores sell full boards.

Formulas used

Board Feet per Piece ¹

BF_{piece} = \frac{T_{in} \times W_{in} \times L_{ft}}{12}

Total Board Feet, MBFT and Lineal Length

BF_{total} = N_{pieces} \times BF_{piece}, \quad MBFT = \frac{BF_{total}}{1000}, \quad LF = N_{pieces} \times L_{ft}

Quantity with Waste Allowance

N_{order} = \left\lceil N_{pieces} \times \left(1 + \frac{w}{100}\right) \right\rceil, \quad \text{Cost} = N_{order} \times P_{piece}

Price Unit Conversion (anchored on price per piece)

P_{piece} = P_{BDFT} \times BF_{piece}, \quad P_{BDFT} = \frac{P_{piece}}{BF_{piece}}, \quad P_{MBFT} = 1000 \times P_{BDFT}, \quad P_{LF} = \frac{P_{piece}}{L_{ft}}

Framing Stud Count

N_{studs} = \left\lceil \left( \left\lceil \frac{R}{s} \right\rceil + 1 + 4 D + 4 W \right) \times \left(1 + \frac{w}{100}\right) \right\rceil, \quad R = 2(L + W_{room}) \ \text{or}\ L

Plate Pieces and Total Lineal Lumber

N_{plates} = \left\lceil \left\lceil \frac{R \times (p+1)}{L_{stock}} \right\rceil \times \left(1 + \frac{w}{100}\right) \right\rceil, \quad LF_{total} = N_{studs} \times H + R (p+1)\left(1+\frac{w}{100}\right)

Boards at Stock Length and Off-cut

n_{per} = \left\lfloor \frac{L_{stock}}{H} \right\rfloor, \quad N_{boards} = \left\lceil \frac{N_{studs}}{n_{per}} \right\rceil + \left\lceil \frac{LF_{plate}}{L_{stock}} \right\rceil, \quad \text{offcut} = L_{stock} - n_{last} H

Sheet Goods Required

N_{sheets} = \left\lceil \frac{A \times \left(1 + \frac{w}{100}\right)}{A_{sheet}} \right\rceil, \quad A_{covered} = N_{sheets} \times A_{sheet}

Frequently asked questions

How many board feet are in a 2x4x8?

Board feet for lumber 1 inch or thicker are normally figured on the nominal thickness and width and the actual length.¹ For a 2×4×8 that is (2 × 4 × 8) ÷ 12 = 5.33 board feet.

The wood's actual volume, using the dry size of 1.5 in × 3.5 in, is (1.5 × 3.5 × 8) ÷ 12 = 3.5 board feet. The Board Footage tab multiplies whatever thickness and width you enter, so enter 2 and 4 to match a yard's count. Ask your yard which size they use before you compare prices.

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

A board foot measures volume. It is 1 in thick, 12 in wide, and 12 in long.¹ It counts thickness, width, and length.

A linear foot (also called lineal foot) only measures length. A 10 ft 2×4 and a 10 ft 2×12 are both 10 linear feet, but the 2×12 holds about three times more wood.

How do you convert linear feet to board feet?

Multiply the thickness (in) by the width (in), divide by 12, then multiply by your total length in feet.

Example: on its nominal size, a 2×6 gives (2 × 6) ÷ 12 = 1 board foot for every foot of length, so 100 linear feet of 2×6 = 100 board feet. On its dry dressed size of 1.5 × 5.5 in, the actual wood volume is 0.6875 board feet per foot, or 68.75 board feet for 100 linear feet.

How many board feet are in a cubic meter?

One cubic meter holds about 424 board feet. One board foot equals about 0.00236 m³.

To go from board feet to cubic meters, multiply by 0.00236. To go the other way, multiply cubic meters by 424.

What does 4/4 mean in hardwood lumber?

Hardwood thickness is written in quarters of an inch. The top number is how many quarter inches thick the rough board is.

4/4 = 1 in rough.
5/4 = 1.25 in rough.
6/4 = 1.5 in rough.
8/4 = 2 in rough.

After surfacing on two sides, a 1-inch (4/4) rough hardwood board is 13/16 in thick.² Board foot pricing is normally based on the rough thickness.

How long is a stud for an 8 foot wall?

Most 8 ft walls use a 92 5/8 in precut stud. Add the 1.5 in sole plate and two 1.5 in top plates, and the wall stands 97 1/8 in tall.

That extra height leaves room for the floor and ceiling drywall, so a 96 in sheet still fits with no cutting.

How many studs do I need for a 20 foot wall at 16 inches on center?

Change 20 ft to inches: 20 × 12 = 240 in. Divide by 16 = 15 spaces. Add 1 stud for the end: 16 studs.

Then add more for the real wall: about 4 extra studs for each door or window, 2 to 3 for each corner, and roughly 10% extra for waste and bad boards.

Why is lumber sold in 8, 10, 12, 14, and 16 foot lengths?

Softwood lumber is made in 1-foot length multiples, and in practice 2-foot multiples in even numbers are common for construction lumber.²

Even lengths divide cleanly by 16 in and 24 in stud spacing, and by the 4 ft width of plywood and drywall. A 16 ft plate spans twelve 16-inch stud spaces with no leftover.

That keeps cuts simple and cuts down on scrap. Odd lengths like 9 or 11 ft are special order at most yards.

How many sheets of plywood do I need for a 12 by 16 foot floor?

The area is 12 × 16 = 192 ft². One 4 × 8 sheet covers 32 ft². So 192 ÷ 32 = 6 sheets.

Buy 7 sheets. Cuts at the walls and staggered seams always waste some panel, so add about 10%.

Is OSB or plywood better for sheathing?

OSB costs less and comes in bigger sheets. It is fine for walls and roofs that stay dry.

Plywood dries faster after it gets wet, holds screws a bit better, and stays flatter. It is the safer pick for floors, roofs that may sit open in rain, and damp areas.

Both meet code for sheathing at the same thickness.

What is the difference between green and kiln dried lumber?

Green lumber is fresh cut and still full of water. It is heavier, cheaper, and it shrinks, twists, and splits as it dries.

Kiln dried (KD) lumber is dried in a heated chamber.² Softwood boards and dimension lumber sold as dry have a moisture content of 19% or less.² It is lighter, straighter, and holds its size. Use kiln dried for framing, trim, and anything you finish indoors.

How much does an 8 foot 2x4 weigh?

A dry spruce, pine, or fir 2×4 at 8 ft weighs about 9 to 10 pounds (4 to 4.5 kg).

Green or pressure treated boards are much heavier because of the water in them. A wet treated 8 ft 2×4 can weigh 17 to 20 pounds. It loses weight over a few months as it dries.

How do you figure out how many deck boards you need?

Take the deck width in inches and divide it by one board width plus the gap. A 5.5 in board with a 1/4 in gap covers 5.75 in.

Example: a 12 ft wide deck is 144 in. 144 ÷ 5.75 = 25.04, so you need 26 rows. Multiply 26 by the deck length to get your total linear feet, then add 10% for cuts, or 15% if the boards run on a diagonal.

Sources

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