How to use this calculator
Start by selecting the thickness of your lumber using the quarter system dropdown. If you are buying rough lumber, leave the surface toggle on Rough. If your boards have already been planed on all four sides, switch to Surfaced (S4S) so the calculator uses the reduced thickness.
Enter the width of each board in inches. If the board width includes a fraction (for example, 5 3/4 inches), enter 5 in the whole number field and select 3/4 from the fraction dropdown. Enter the length in feet and any extra inches.
Use the quantity field if you have multiple boards with the same dimensions. For boards with different sizes, click "Add Another Board" to create a separate entry for each one.
Optionally, select a wood species to see an estimated weight for your order, and enter a price per board foot to calculate total cost. The waste factor defaults to 10%, which accounts for cuts, defects, and unusable sections. Adjust it higher for complex projects.
Understanding the quarter system
Hardwood lumber thickness is expressed in quarters of an inch. A board labeled 4/4 (said as "four quarter") is 1 inch thick in its rough state. 8/4 ("eight quarter") is 2 inches thick. This system has been the standard in the hardwood industry for over a century.
The quarter designation always refers to the rough sawn thickness. Once a board is surfaced (planed smooth), it loses about 1/4 inch of total thickness. So a 4/4 board that starts at 1 inch will finish at approximately 3/4 inch after surfacing. When planning a project, always work backward from your finished thickness to determine which quarter size to buy.
How lumber yards price hardwood
Unlike softwood dimensional lumber (2x4s, 2x6s) which is sold by the linear foot or per piece, hardwood is sold by the board foot. This makes sense because hardwood boards come in random widths and lengths. Two boards might be the same thickness and length but one could be 6 inches wide and the other 10 inches wide, so pricing by board foot accounts for the actual amount of wood.
Prices vary widely by species, grade, and your region. Poplar is one of the most affordable domestic hardwoods, while walnut and cherry command premium prices. Exotic species like purpleheart and padauk cost even more. Many yards offer better rates if you buy in volume, so it pays to plan your material list for multiple projects at once if possible.
Frequently asked questions
How do you calculate board feet?
Multiply thickness (in inches) by width (in inches) by length (in inches), then divide by 144. For example, a 1 inch thick board that is 8 inches wide and 8 feet (96 inches) long equals 5.33 board feet. Always use actual measured dimensions rather than nominal sizes.
What does 4/4 mean in lumber?
The quarter system expresses thickness in quarter inch increments. 4/4 means four quarters, or 1 inch thick. 5/4 is 1 1/4 inches, 6/4 is 1 1/2 inches, and 8/4 is 2 inches. These measurements refer to the rough sawn thickness before any planing or surfacing.
What is the difference between rough and surfaced lumber?
Rough lumber has the texture left by the sawmill blade and retains its full nominal thickness. Surfaced lumber (S4S, meaning surfaced on all four sides) has been planed smooth, removing about 1/4 inch of thickness. Many woodworkers buy rough and surface it themselves for better control over the final dimensions.
How much extra lumber should I buy for waste?
Plan for 10% waste on straightforward projects. Increase to 15 or 20 percent if your design has angled cuts, curves, or if you are working with lower grade boards that have more knots and defects to work around. It is always better to have a few extra board feet than to make a second trip to the lumber yard mid project.