Lumber Calculator
Use this free lumber calculator to estimate how many boards you need for a woodworking, framing or construction project. Enter your project length, board spacing and lumber dimensions to calculate board quantity, total linear feet, board feet, waste allowance and estimated lumber cost.
Project layout
Board dimensions
How to estimate lumber for a project
Start with the total length of the area where boards will be installed. Then divide that length by the planned spacing between boards or framing members.
Add one board to account for the starting edge or end member. This gives the basic quantity before waste.
Add a waste allowance for trimming, defects and unexpected cuts. A small project may need only a few percent, while more complex layouts may need a larger allowance.
The calculator also estimates total linear feet and board feet, which can help compare material quantities and costs.
If you only need to calculate lumber volume in board feet, use the Board Foot Calculator. For sheet materials, use the Plywood Calculator.
Example calculation
Project length: 20 ft
Spacing: 16 in
Board length: 8 ft
Waste allowance: 10%
Cost planning
Lumber price estimator
This lumber calculator can also work as a simple lumber price estimator. Enter the price you pay for one board and the calculator multiplies that price by the final quantity of boards needed after the waste allowance is added.
This makes it easier to estimate lumber cost before buying materials and compare different board sizes, lengths or waste allowances for your project.
Lumber prices vary by wood species, grade, dimensions and location, so use the current price from your local supplier for the most useful estimate.
Lumber cost formula
Estimated lumber cost =
Example: if your project needs 18 boards and each board costs $12, the estimated lumber cost is $216.
Lumber calculator FAQs
What does board spacing mean?
Board spacing is the distance from one board or framing member to the next along the project length.
Why does the calculator add one board?
A layout usually needs a starting or ending board in addition to the intervals created by the spacing.
How much waste should I add?
Many projects use a waste allowance of around 5% to 15%, depending on cuts, defects and layout complexity.
Can I estimate lumber cost?
Yes. Enter a price per board and the calculator will estimate the total purchase cost.
How many boards do I need for my project?
Enter the total project length, spacing between boards and board dimensions. The lumber calculator estimates the base number of boards and then adds your selected waste allowance.
How do I estimate the total price of lumber?
Enter the price per board in the calculator. The lumber price estimator multiplies the final number of boards, including waste, by the price per board to estimate your material cost.