Formula developed by the Japanese Ministry of Agriculture and Forestry.

Measuring Log Length

Lengths are measured in metres and tenths of metres and rounded down to each fixed-length class

Measuring Log Diameter

For small-end diameters less than 14 cm
Measure the shortest small-end diameter inside the bark through the centre of the log. Round down to the nearest whole centimetre.
Example: 12.00 - 12.99 cm, enter 12 cm
For small-end diameters equal to and greater than 14 cm
Measure the shortest small-end diameter inside the bark through the centre of the log.
Round down to the nearest even 2-cm interval.
Example: 16.00 - 17.99 cm, record as 16 cm

If the short axis is between 14 and 40 cm, add 2 cm to the short axis for every 6 cm of difference. If the short axis exceeds 40 cm, add 2 cm to the short axis for every 8 cm of difference.

S=16.00 -  L=22.99 cm, record as 18 cm
S=16.00 -  L=32.99 cm, record as 28 cm
S=42.00 -  L=45.99 cm, record as 42 cm
S=41.00 -  L=49.60 cm, record as 43 cm