NHLA CalculatorNHLA Hardwood Grade Calculator
Determine the NHLA hardwood lumber grade from board dimensions and clear yield. Calculate surface measure and estimate FAS, Select or Common grades to the North American standard used worldwide.
Why this calculation matters
Grade decides price and cutting yield together. NHLA measures clear cuttings, not appearance, so a board can look poor and grade well.
NHLA Calculator
NHLA Hardwood Grade Calculator
Usable area free of defects.
Clear pieces needed to reach yield.
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About NHLA Calculator
The NHLA (National Hardwood Lumber Association) grading rules are the global standard for hardwood lumber, used throughout North America and by importers worldwide including India. Grades are based on the percentage of clear, defect-free cuttings obtainable from the poorer face of a board. This tool calculates surface measure and clear yield to estimate the NHLA grade - FAS, Select, or the Common grades. It walks the NHLA grading rules logic — surface measure, clear cuttings — to show whether a board makes FAS lumber grade or drops to Common.
Where Is This Used?
Formulas & Grade Rules
Surface Measure (SM) = (Length_ft x Width_in) / 12, roundedClear yield % = (Clear cutting area / Total face area) x 100FAS: minimum 83.3% clear (10/12)No. 1 Common: minimum 66.7% (8/12)No. 2A Common: 50% (6/12) | No. 3A: 33.3% (4/12)How the calculation works
Grading measures clear cuttings, not appearance. A board that looks poor still grades FAS if the defect-free areas fall in the right sizes and places, which is why grade and looks often disagree.
Show the formula
Surface measure = length in feet x width in inches / 12, rounded. Clear yield = clear cutting area / total area. FAS requires 10/12 of the surface measure (83.3%), No. 1 Common 8/12 (66.7%), and the lower grades follow their own thresholds.Applies the yield thresholds only. Minimum cutting sizes, cutting count limits and grader discretion are not modelled, and only a certified NHLA inspector can grade for sale.
References and what each one provides
- NHLA RulesNational Hardwood Lumber AssociationSurface measure, clear-cutting requirements and grade thresholds in twelfths.
Unverified values are marked as such rather than presented as sourced.
Limitations of this calculation
Applies NHLA cutting rules to the dimensions entered. It does not account for defect placement within the board, wane, warp, or the grader discretion permitted within the rules.
Do not use this for Official grade certification, inspection certificates, or dispute resolution. Only a certified NHLA inspector can grade for sale.
Figures are engineering estimates from the inputs and assumptions shown. Verify against the actual material and, where the result affects structure or safety, against a qualified professional.
- NHLA: SM = (Length_ft × Width_in) / 12, rounded
- Grade thresholds in twelfths — FAS 10/12, No.1C 8/12, No.2C 6/12, No.3C 4/12
Formula checked against the sources above by an automated regression test (tests/verify-phase3a.js) that derives each expected value independently of this page. Last reviewed .
How to use this tool
- Enter the trade details below, then press Calculate.
- Fill in board length, board width, clear (defect-free) area, number of cuttings.
- Press Calculate.
Worked example
Common mistakes to avoid
- Measuring the board face in inches instead of the NHLA surface-measure convention. Follow the rule's own method.
- Grading from the best face. NHLA grades most lumber from the poorer face — the opposite of what feels natural.
- Counting cuttings that are too small. Each grade has a minimum cutting size; smaller clear areas do not count.
Frequently Asked Questions
Wood species data
Density, hardness and movement for 60 timbers