"Cubic method" log volume formula for estimating the volume of a log using one diameter small end measurement. This is one of the methods of log scaling used in Manitoba, Canada, the other one is the Smalian formula.

Cube Method: Log Volume in Cubic Metres of Tapering Cylinders

V = volume in cubic metres (m³)
π = 3.14159
L = length of log in metres
D = small end diameter of log in centimetres

Log Length

Lengths are entered in the odd centimetre class with the class boundary occurring on the even centimetre.
example:
Logs greater than 3.4 m in length and up to and including 3.6 m in
length, are entered as 3.5 m logs.
a log 3.4 m in length is entered as 3.3m
a log 3.61 is entered as 3.7m

Log Diameter

Diameters are measured inside the bark in 2 centimetre size class intervals, with the class boundary occurring on the odd centimetre,
example
33 cm to 35 cm diameter is entered as 34cm
35.1 cm diameter is entered as 36 cm