Board Foot Calculator

A board foot measures volume, not area or length. This distinguishes it from square footage, which measures a flat surface, and linear footage, which measures a straight distance regardless of width or thickness. Lumber has all three dimensions, so a measurement based on length alone would not reflect how much wood is actually being bought.

By definition, one board foot equals a piece of wood measuring 1 foot long, 1 foot wide, and 1 inch thick. This works out to 144 cubic inches. A board of any shape or size can be converted to board feet as long as its length, width, and thickness are known.

Lumber is priced by volume rather than by the piece because boards vary widely in size. A single wide, thick board can contain more usable wood than several narrow, thin ones. Pricing by board foot lets buyers and sellers compare cost consistently across different board dimensions, rather than paying a flat per-board rate that ignores size.

Board foot is an imperial-based lumber measurement standard, and it remains the standard even in countries that use metric units for most other measurements. There is no widely adopted metric equivalent in the lumber trade, so buyers working in metric-based markets still need to convert their measurements to feet and inches to calculate board footage accurately.

The standard board foot formula is:

This version of the formula requires length in feet, while width and thickness are entered in inches. Mixing up these units is the most common source of calculation error, so it is worth checking each field before relying on the result.

If all three dimensions are measured in inches instead, use this version:

Both formulas produce the same result. The difference in the divisor, 12 versus 144, accounts for the unit conversion between feet and inches. Choose whichever formula matches the units already on hand, rather than converting measurements unnecessarily.

In the hardwood trade, thickness is commonly rounded up to the nearest quarter inch, a convention tied to how lumber is graded and sold in quarters (4/4, 6/4, 8/4, and so on). This is a trade convention rather than a universal mathematical rule, and it does not apply to every calculator or every supplier. Anyone comparing board footage across sources should confirm which rounding method, if any, was used.

The calculator above requires four inputs: number of boards, thickness, width, and length. Enter the dimensions of a single board, then set the number of boards to match your order. The calculator applies the same dimensions across all boards entered, so if your order includes boards of different sizes, calculate each size separately and add the results together.

Thickness and width should be entered in inches, and length in feet, unless the calculator specifies otherwise. Most fields accept either decimal values (8.25) or fractional values (8 1/4), so enter measurements in whichever format matches how they were taken. Leave a space between a whole number and a fraction if entering fractional values, so the field reads the entry correctly.

Once the required fields are filled in, the calculator returns the total board feet for the order, calculated using the board foot formula and the number of boards entered. This figure represents the total lumber volume, not the number of pieces or the surface area covered.

An optional price per board foot field is also available. If a price is entered, the calculator multiplies it by the total board feet to produce a total cost. Leaving this field blank returns board footage only, with no cost calculation.

The following example walks through a typical lumber project calculator use case. The figures below are for illustration only, and the price used is a placeholder rather than a fixed currency default, since actual lumber pricing varies by species, supplier, and region.

This same process applies whether the calculator is being used for a single woodworking lumber calculator project or a larger order handled through a contractor lumber calculator workflow. The board feet per piece figure stays consistent regardless of quantity. What changes is the multiplier applied at the final step, whether that is number of boards, price, or both. Anyone using the tool as a lumber cost estimator for a DIY lumber calculator project can follow the same five steps, entering their own dimensions and price in place of the example values.

Board foot is often confused with linear foot and square foot, since all three use "foot" in the name. Each measures something different, and using the wrong one leads to inaccurate estimates.

A board foot vs linear foot comparison comes up most often with trim and molding, which are typically sold by linear foot since their width and thickness are fixed and only length varies. A board foot vs square foot comparison comes up with flooring and paneling, which are sold by the area they cover rather than by volume, since thickness is usually standardized across the product line.

Lumber sold in dimensional sizes with variable thickness, such as rough-cut hardwood, is measured in board feet because volume is what determines how much material is actually being purchased. A linear foot calculator or a square footage calculator is useful for working out the area a project covers when a specification is given by coverage rather than by volume, but board foot remains the standard board foot measurement wherever lumber volume, rather than length or coverage, determines cost.