NHLA Measurement Rules: Surface Measure, Board Feet and Tally Rounding

NHLA measurement turns a board into two numbers. Surface measure (SM) is the face area in square feet, rounded to a whole number, and it decides how many cuttings a grade allows. Board feet (BF) is SM multiplied by the thickness in inches, and it is what you pay for. Everything on a tally follows from those two steps and from the rounding rules in the NHLA rulebook.

Item	Typical rule (as of October 2026)
Rulebook	NHLA Rules for the Measurement and Inspection of Hardwood and Cypress
Rule review	Every four years. Approved changes take effect 1 January of the following year
Latest edition confirmed	2023, effective 1 January 2023 (publication listings; the rulebook text was not available for this review). Check nhla.com for a newer edition
Surface measure	Width in inches x length in feet / 12, whole number
Board feet	Surface measure x thickness in inches
Thickness	Named in quarters on rough lumber: 4/4 = 1 in, 8/4 = 2 in
Grade basis	Surface measure, not board feet, so thickness does not change the grade

The NHLA rulebook governs. Figures below are typical and come from published summaries of the rules, not from the rulebook text.

From board to tally in four steps

1. Measure the width. The board is measured in inches and fractions. In the usual summary of the rule, fractions are rounded to the nearest whole inch, and a fraction of exactly one half is rounded up one time and down the next, so the count does not favor either side over a large lot.
2. Measure the length. Lengths are counted in whole feet. For export tallies the American Hardwood Export Council describes lengths as always rounded down to the whole foot. The rulebook has its own wording for odd lengths and for short grades, so do not assume the export summary covers a domestic contract.
3. Work out surface measure. Width x length / 12, rounded to a whole number. A board 6 1/4 in wide and 8 ft long gives 4 SM.
4. Multiply by thickness. SM x thickness in inches gives board feet. At 8/4 the 4 SM board is 8 BF. At 4/4 it is 4 BF.

The tally adds the board feet of every board in a bundle or load. Because each board is rounded on its own, a tally total is not the same as total volume divided by 144 cubic inches. When a buyer checks a quote by multiplying a pack’s average width by its length, small differences are normal. A large difference points to a different rounding rule, a different thickness basis or a counting error.

Thickness is measured on the rough board

Quarters	Rough thickness	Metric
3/4	3/4 in	19.0 mm
4/4	1 in	25.4 mm
5/4	1 1/4 in	31.8 mm
6/4	1 1/2 in	38.1 mm
8/4	2 in	50.8 mm
10/4	2 1/2 in	63.5 mm
12/4	3 in	76.2 mm
16/4	4 in	101.6 mm

Surfaced lumber is still tallied on the nominal rough thickness in the usual trade practice. The American Hardwood Export Council summary gives the typical surfaced thickness as 3/16 in less than nominal for lumber up to 1 1/2 in and 1/4 in less for lumber 1 3/4 in and thicker. A 4/4 board surfaced on two sides therefore arrives near 13/16 in and is still tallied as 1 in. If your part must finish at a full inch, order 5/4. Our guide to board feet and quarter thickness works through the price side of this.

Green tally and net tally

Lumber shrinks as it dries, and the tally changes with it. A gross or green tally measures the boards before drying. A net tally measures them after kiln drying. The same source puts the loss at roughly 7 percent fewer board feet after drying, which is why a green quote and a kiln-dried quote cannot be compared until both are on the same basis. Kiln-dried stock also carries a scant allowance in thickness and width in the rules. The hardwood lumber tally guide shows the arithmetic.

What a tally must show

A tally that a buyer can check carries these lines, whatever format the mill uses:

• Species by botanical name and the trade name.
• The grade and the rule it was graded to, with the edition.
• Thickness in quarters, and whether it is rough or surfaced.
• Moisture condition: kiln dried, air dried or green, with the target range.
• Each bundle with its piece count, widths and lengths or a width and length summary, and its board feet.
• The totals per bundle and per load, and whether they are gross or net.
• The rounding rule used for widths and lengths.

Our lumber tally sheet guide shows a sample layout.

Where tally disputes start

Cause	What happens	Fix
Rough versus surfaced basis	One quote counts the 13/16 in thickness, another counts 1 in	State the thickness basis on the quote
Gross versus net	Green board feet compared with dried board feet	Ask for the net tally after drying
Rounding rule	Two mills round half inches differently	Name the rule and edition in the contract
Unit	Board feet against cubic meters	Convert once, on the quote: 1 MBF is about 2.36 cubic meters
Edition	Rule changes between editions	Name the edition

What to write on the RFQ

State the rule and edition for measurement and grading, the thickness basis, and whether you want a net tally after drying. Ask for a tally by bundle that matches the packing list. Then send your lumber RFQ and we pass it to up to 3 mills or yards that say they can quote on that basis.

RFQ line: Red oak (Quercus rubra), No.1 Common, 4/4 rough, KD 6-8%, measured and graded to NHLA rules, edition named, net tally by bundle.