Lumber Yield Calculator
When buying rough hardwood lumber, the stated board footage reflects the gross size of the board before milling and defect removal. The usable (net) board footage available for your project depends on the grade of the lumber and how efficiently you can cut around defects. This calculator converts gross board feet into net usable board feet using a yield percentage. It also calculates how many gross board feet you need to purchase to have a target number of net board feet available, given a yield percentage.
Lumber yield formula
Net BF = Gross BF × (Yield% / 100)
Gross BF needed = Target net BF / (Yield% / 100)
Yield percentage is the fraction of purchased lumber that ends up as usable, defect-free material after surfacing and defect removal. The NHLA grades define minimum yield percentages by grade. Multiply gross board feet by the yield fraction to get net board feet. Divide target net board feet by the yield fraction to get how much to purchase.
NHLA hardwood lumber grades
- FAS (Firsts and Seconds): minimum 83.33% clear cuttings. Best grade, widest boards, fewest defects.
- FAS One Face (F1F): FAS on one face, No. 1 Common on the other. Good for projects showing only one face.
- Select: similar to FAS but allows narrower boards (4 to 6 inches wide).
- No. 1 Common: minimum 66.67% clear cuttings. Good general-purpose grade for furniture.
- No. 2 Common: minimum 50% clear cuttings. Economical grade for smaller parts or painted work.
Lumber yield calculator: frequently asked questions
What is a typical yield percentage for rough hardwood lumber?
Yield depends on grade, species, and the size of parts being cut. FAS (Firsts and Seconds) grade hardwood typically yields 83 to 100 percent clear cuttings. No. 1 Common grade yields 66 percent. No. 2 Common yields 50 percent. These are the National Hardwood Lumber Association (NHLA) grading minimums.
How much thickness is lost when surfacing rough lumber?
Rough 4/4 lumber (nominally 1 inch) is typically 1-1/16 to 1-1/8 inches thick. After surfacing two sides (S2S) to 13/16 inch, about 1/4 inch is removed. If you need a finished 3/4-inch thickness, you typically start with 4/4 rough stock.
Does the grade affect usable length or just width?
NHLA grading allows clear cuttings to come from any part of the board, including short pieces. Grade limits the minimum size of each clear cutting, not the total board length. In practice, end checks, knots, and wane reduce usable length on lower grades.
Should I account for kerf loss in the yield calculation?
This calculator uses an overall yield percentage that already accounts for the combined effect of surfacing loss, defect removal, and kerf waste in typical cutting. If you want to separate these factors, use the wood shrinkage and kerf spacing calculators alongside this one.
How do I estimate yield for figured or highly defective wood?
Highly figured wood or boards with heavy mineral staining, worm holes, or checks may yield less than the NHLA grade minimum. Inspect boards individually and estimate clear area visually. Factors of 40 to 60 percent are common for very rough-graded material.
Official sources
- USDA Forest Products Laboratory: Wood Handbook, FPL-GTR-190 (lumber grading).
- USDA Forest Service: Forest Service Homepage.
Reviewed by the CalculatorHub team, edited by James Graham, 15 June 2026. See our methodology.