Giving you the Edge in Business

This rule is also termed the United American Investigation Form. This revised formula seems to be rarely used.
The revised JAS formula for Logs under 6 meters is the same as the standard JAS formula.
The revised JAS formula applies to logs 6 meters and longer is modified by including a factor, f, to adjust the original taper assumption. For 6 meter and longer logs, the volume in cubic meters is determined as:
First:
LX = is the length rounded down to the nearest meter and the term (LX – 4) / 2 is a taper adjustment of 1 cm per meter of length (about 1 inch per 8 feet). This formula views a log as a square cant with a side equal to the scaling diameter.
The revised version introduces a factor (f) that modifies the taper adjustment depending on the diameter of the log.
The revised equation is:
Cubic Meters: M³ = ((D + ((LX – 4) / 2) * f )²) x L) /10,000
where f
= 0.6 if D > 28 cm
= 0.8 if D > 30 and < 58
= 1.0 if D > 60 cm.
Note that for logs over 60 cm in diameter there is no difference between the JAS and the JAS revised rules.

Example 1:
10.40 meter log; small diameter = 35cm.
LX = 10 (length rounded down to nearest meter).
LX - 4)/2 = (10 - 4) / 2 = 3 f = 0.8 M³ = (((35 + (3 * 0.8))²) x 10.4) / 10,000 = (((37.4)²) x 10.4) / 10,000 = 1.455 M³

Example 2:
Length = 13.4; Diameter = 26 cm
LX = 13 (length rounded down to nearest meter).
(LX - 4)/2 = (13 - 4) / 2 = 4.5
f = 0.6
M³ = (((26 +(4.5 * 0.6))²) x 13.4) / 10,000 = (28.7)² x 13.4 / 10,000 = 1.104 M³