Board Foot Calculator – Lumber, Boards, and Log Rules

Also see: Dimensional Lumber Weight Calculator

What Are Board Feet and Why Are They Used?

A board foot is a unit of volume used to measure lumber and logs in the United States and Canada. One board foot represents the amount of wood contained in a piece that is 1 inch thick, 12 inches wide, and 12 inches long. Any piece of wood that has that same volume, regardless of its shape or dimensions, equals one board foot.

Board feet are used because wood products rarely share the same thickness, width, and length. Linear feet describe length only, and square feet ignore thickness altogether. By expressing wood volume in board feet, different lumber sizes can be compared, priced, and totaled using a single standardized unit, making board feet especially useful anywhere lumber is bought, sold, milled, or estimated.

Board feet are commonly used by:

• Sawmills and lumber yards when pricing rough or dimensional lumber
• Woodworkers and furniture builders estimating material requirements
• Contractors ordering framing lumber or specialty wood products
• Foresters and log buyers scaling logs prior to milling
• Anyone comparing lumber of different sizes on an equal basis

When applied to logs, board feet are not a direct physical measurement. Instead, they represent an estimate of the amount of sawn lumber that can be recovered from a log based on its diameter and length. Different log rules exist because real-world milling losses vary due to saw kerf, log taper, slab waste, and milling methods.

Board feet are commonly abbreviated as BF, BDFT, or FBM (short for “foot, board measure”). Larger quantities are often expressed in thousands of board feet, written as MBF, MBFT, or MFBM, depending on industry or regional convention.

Board Foot Calculator

Board Foot Calculator

Board Foot Calculator

Calculate board feet from boards, estimate boards from board feet, or scale logs using common log rules.

Turn pricing mode on

What do you want to calculate? Board feet from boards (I know board size and quantity) Board feet from logs (use a log rule) Boards from board feet (I know board feet and want an equivalent board count)

What do you want to do? Each option uses a different set of inputs.

How are the boards sized? Standard nominal lumber size (for example, 2×6) Actual measured dimensions (thickness and width)

Nominal sizes use typical actual dimensions for surfaced lumber.

Board sizes:

Add one or more board entries. Each row represents a group of identical boards.

Boards

Add board size

Tip: Add a board size entry for each group of boards with the same thickness, width, and length. Inputs accept decimals. Inch inputs also accept fractions, with spaces or hyphens (for example, 7/16, 3 1/2, or 16-1/4). Quantity must be a whole number.

Calculate Clear

Results

Total board feet: –

Total boards: –

Average board feet per board: –

Equivalent volume: –

Board foot calculator page URL:

Copy results Share results URL Print results

How to Use This Board Foot Calculator

There are three ways to use this calculator, based on what you are trying to do and what information you’re starting with. If you just want a quick result, select a mode, enter your measurements, and press Calculate. It's actually pretty simple. The more detailed instructions below explain all the options if you need them.

Mode Selection: “What do you want to calculate?”

At the top of the calculator, choose one of the following modes:

• Board feet from boards
  Use this when you know the board sizes, lengths, and quantities and want to calculate total board feet.
• Board feet from logs
  Use this when you know log diameters and lengths and want to estimate board feet using a log rule.
• Boards from board feet
  Use this when you know the total amount of board feet and want to estimate how many boards of a specific cross-section and length that that amount equals.

Each mode shows only the inputs relevant to that calculation.

Pricing Mode (optional total cost calculation)

You can use the calculator either for quantity only or for quantity plus cost.

Turn pricing mode on or off using the pricing toggle button near the top of the calculator. When pricing mode is turned on, additional price-related fields appear and the results area will include Total cost and a detailed breakdown. When pricing mode is turned off, those fields are hidden and the calculator will only show board-foot and quantity results.

When pricing mode is on, enter any pricing values you want to include, such as cost inputs, discounts, or sales tax. Leaving the optional discount and tax fields blank treats those inputs as zero.

Total cost is always calculated from the same board-foot results produced by the selected mode.

Board Feet From Boards Mode

This mode calculates board feet from one or more groups of boards.

Board Size Input Method

You must first choose how board size is defined:

• Standard nominal lumber size
  Uses typical surfaced lumber dimensions. For example, a nominal 2×6 is treated as 1.5 inches by 5.5 inches.
• Actual measured dimensions
  Allows you to enter the true thickness and width in inches. This is useful for rough-sawn lumber or nonstandard material.

This selection will apply to all board rows that you create during the calculation.

Read more about nominal vs. actual lumber dimensions and why they're different.

Board List

Each board row represents a group of identical boards.

For each row, enter:

• Thickness and width
  Either selected from the nominal list or entered manually as actual dimensions.
• Board length
  Enter feet and inches separately. Inches may be decimals or fractions such as 3 1/2 or 3-1/4.
• Quantity
  Must be a whole number and represents how many identical boards are in that group.

You may add as many rows as needed to represent different sizes, lengths, or quantities.

How the Calculation Works

For each board, board feet are calculated as:

Thickness × Width × Length ÷ 12

Each row’s total board feet are summed to produce the overall total.

Results Explained

• Total board feet
  The combined board feet of all boards entered.
• Total boards
  The total quantity of boards across all rows.
• Average board feet per board
  Total board feet divided by total board count. When multiple board sizes or lengths are entered, this is an average only and will not usually match any single board exactly.
• Equivalent volume
  The total volume expressed in cubic feet (and cubic yards in the breakdown).
• Total cost
  Shown only when pricing mode is turned on. This is the calculated cost after applying any pricing inputs you entered.

The breakdown section shows the calculation for each row and the board feet per individual board.

Boards From Board Feet Mode

This mode estimates how many boards you can get from a known board-foot total.

Required Inputs

• Total board feet
  Your known target total board feet.
• Board size for this calculation
  Either a nominal size or actual thickness and width.
• Board length
  Entered in feet and inches, just like the board list.

How the Calculation Works

First, the calculator determines how many board feet one board of the specified size and length contains. Then it divides the total board feet by the board feet per board.

Results Explained

• Estimated board count
  The calculated number of boards of the selected size and length.
• Board feet entered
  The total board feet you supplied.
• Board feet per board
  The amount of board feet in one board of the selected dimensions.
• Equivalent volume
  The total volume represented by the board feet.
• Total cost
  Shown only when pricing mode is turned on. This is the calculated cost after applying any pricing inputs you entered.

The estimated board count result may include partial boards. This is a mathematical estimate, not a cutting list, and real-world cutting will always round to whole boards.

Board Feet From Logs Mode

This mode estimates board feet from logs using traditional log scaling rules.

Log Rule Selection

This calculator can estimate board feet from logs using three traditional log rules. These rules were developed before computers. Each one uses slightly different assumptions about taper, slab loss, kerf, and waste, so the same log can give different results under different rules.

Choose one of the following:

Doyle

Often required in some regions for buying and selling logs.

• Tends to undervalue smaller logs because it assumes heavy waste
• Can overvalue large logs
• Commonly used in parts of the eastern United States

Doyle results usually give the lowest estimate of the three rules, especially for small-diameter logs.

Formula

Board feet = $(D − 4)^2 × L$(D−4)2×L ÷ 16

Where D is the small-end diameter inside bark in inches and L is the log length in feet. Logs 4 inches and under calculate as zero under this rule.

Scribner (Decimal C)

A long-standing rule that attempts to estimate how many boards can actually be sawn from a log.

• Often gives higher estimates than Doyle
• Moderately accurate on medium-size logs
• Still used in many timber sale contracts and stumpage agreements

Scribner is a middle-ground option that many mills and foresters are familiar with.

Formula (Decimal C approximation)

Board feet = $(0.79D^2 − 2D − 4) × L$(0.79D2−2D−4)×L ÷ 16

Where D is the small-end diameter inside bark in inches and L is the log length in feet.

International 1/4-inch

Designed to be a more accurate rule over a wide range of log sizes.

• Assumes a 1/4-inch kerf saw
• Accounts more carefully for taper and waste
• Generally produces the most realistic estimate of actual lumber output

For this calculator, log length is rounded down to the nearest 4-foot section, because International 1/4 is traditionally applied in 4-foot segments.

Formula

For each 4-foot segment:

Board feet = $0.22D^2 − 0.71D$0.22D2−0.71D

For logs longer than 4 feet:

Board feet = $(0.22D^2 − 0.71D) × (L ÷ 4)$(0.22D2−0.71D)×(L÷4)

Where D is the small-end diameter inside bark in inches and L is the log length rounded down to the nearest 4 feet.

You may see the International 1/4 rule written in other algebraic forms using A, B, and C constants. This calculator uses the common 4-foot segment version of the rule, which is mathematically equivalent to those forms.

Which rule should you choose?

• Use the rule your mill, buyer, or contract specifies
• Choose Doyle for a conservative or low estimate
• Choose International 1/4-inch for the closest estimate to likely yield
• Choose Scribner if you want results consistent with older tables or paperwork

All log rules are estimates. Real-world results depend on defects, taper, sweep, grade, sawing pattern, and mill efficiency.

Log List

Each log row represents a group of identical logs.

For each row, enter:

• Small-end diameter inside bark (DIB)
  Measured at the smaller end of the log, in inches. Fractions are allowed.
• Log length
  Entered in feet.
• Quantity
  The number of identical logs in that group.

You may add as many rows as needed to represent different sizes, lengths, or quantities.

How the Calculation Works

The calculator applies the selected log rule to each log, then multiplies by quantity. For International 1/4, log lengths are rounded down to the nearest multiple of 4 feet before calculation, and longer logs are scaled in 4-foot segments.

Results Explained

• Total board feet
  The estimated board feet across all logs.
• Total logs
  The total number of logs entered.
• Average board feet per log
  This is the total board feet divided by the number of logs. If you entered logs of different sizes or lengths, this number is just a mathematical average. It will not necessarily equal the board-foot value of any one log.
• Equivalent volume
  The total volume expressed in cubic feet (and cubic yards in the breakdown).
• Total cost
  Shown only when pricing mode is turned on. This is the calculated cost after applying any pricing inputs you entered.

Each log line in the breakdown shows the diameter, entered length, quantity, and total board feet for that group. When International 1/4 is selected, the rounded length actually used is clearly indicated.

Notes and Practical Considerations

• Board-foot units represent wood volume, not finished lumber yield. Actual usable lumber may be lower due to drying shrinkage, planing, defects, or trimming.
• When applied to logs, board-foot estimates are not physical measurements. Log rule results can vary significantly and may differ from actual mill output depending on log quality, taper, sawing method, and mill efficiency.
• Different log rules are based on different assumptions about saw kerf and waste. As a result, the same log may produce noticeably different board-foot estimates under different rules.
• Nominal lumber sizes use standard surfaced dimensions, not their stated nominal dimensions. For example, a nominal 2×6 is treated as 1.5 inches by 5.5 inches unless actual dimensions are entered.
• Actual dimension inputs are useful for rough-sawn lumber, reclaimed material, or nonstandard stock, where nominal sizing conventions do not apply.
• All inch inputs accept fractions and mixed numbers, including formats with spaces or hyphens. This allows measurements to be entered as they are commonly taken in the field.
• Lengths are treated as exact entered values unless otherwise noted by the selected log rule. Some log rules round or segment log lengths as part of their calculation method.
• Quantities must be whole numbers, since partial boards or logs are not physically meaningful in most material estimates.
• Results are calculated mathematically and should be interpreted as planning or estimating tools. Actual yield or cost may differ due to waste, defects, mill practices, taxes, delivery charges, or market pricing.

This calculator is designed to reflect real-world lumber measurement and log scaling practices while remaining flexible enough to handle mixed sizes, rough lumber, and multiple entries.

Sharing, Copying, and Printing Results

After you run the calculator, you will see three helpful options: Copy results, Share results URL, and Print results. These do not change your numbers; they simply make it easier to save or send what you calculated.

Copy results

This button copies a neatly formatted summary of your calculation to your clipboard.

The summary includes:

• the main results
• the inputs you used
• the line-by-line breakdown

You can then paste it into an email, text message, document, etc.

Share results URL

This button creates a link to this calculator with your information already filled in. The link does not just save your answers. It also restores the calculator mode and options you were using.

You can send this link to anyone. When they open it, the calculator will:

• already be set to the same mode you used
• already contain the same boards, logs, sizes, and quantities you entered
• already have the same prices, discounts, and tax rates if you used pricing mode
• already display your calculated results

In other words, the calculator opens showing your exact scenario, and the other person can change anything they like without re-entering everything from scratch.

There is a practical limit on how much information can fit into a link. If your list of boards or logs is extremely long, the calculator will simply let you know that the link is too long to create. In that case, you can still use Copy results or Print results.

Print results

This option gives you a clean, printer-friendly page that shows:

• the calculator page address
• your results
• your inputs

Further Reading and References

• Wood Handbook: Wood as an Engineering Material (Forest Products Laboratory) – Comprehensive technical reference covering wood properties, volume measurement, lumber dimensions, milling losses, and how wood volume relates to finished products.
• National Forest Log Scaling Handbook (USDA Forest Service) – Detailed explanation of log scaling principles, diameter and length measurement, common log rules, and sources of variation between estimated and actual yield.
• Log and Tree Scaling Techniques (Purdue Extension) - PDF guide covering multiple log rules, their history, and how board-foot estimates are derived.
• Measurement of Forest Products (FAO) – International overview of timber measurement systems, including volume units, conversion methods, and how different regions quantify wood products.
• National Hardwood Lumber Association Rules for the Measurement and Inspection of Hardwood Lumber – Industry-standard rules defining how hardwood lumber is measured, graded, and sold, including board foot calculations and inspection practices.
• Measuring Standing Trees (Ohio State University Extension) - Clear explanation of board feet and tree volume estimation using log rules, suitable for landowners and forestry students.
• American Softwood Lumber Standard (American Lumber Standard Committee) – Authoritative standards governing softwood lumber dimensions, nominal versus actual sizes, and measurement conventions used in commerce.
• Timber Cruising Handbook (Washington Department of Natural Resources) – Practical guidance on estimating standing timber volume, log scaling concepts, and how board foot estimates are developed before harvesting.
• Timber Scaling Manual (British Columbia Ministry of Forests, Lands and Natural Resource Operation) – Government manual explaining log scaling, timber measurement systems, and regulatory practices used in commercial forestry operations.
• Understanding Timber as a Commodity (SC Forestry Commission) - Government landowner resource discussing how board feet are used commercially and how different log rules affect timber value.
• Timber Products Monitoring: Unit of Measure Conversion Factors for Roundwood Receiving Facilities (USDA Forest Service) – Reference material on converting between board feet, cubic volume, weight, and other wood measurement units used in forestry and industry.