Measurement of round timber for sale purposes in Ireland.
The volume of Irish logs is calculated using Huber's formula.

Diameters are measured mid-length of the log over bark in centimetres (cm)
Lengths are measured in metres (m) to the nearest centimetre.
A log whose length is greater than 20 metres has to be divided into two lengths for the purpose of calculating the log volume.

Huber's Formula:

V = (π  * Dm²) ÷ 40000 * L

V = volume in cubic metres (m³)
π = 3.1416
Dm = mid-diameter (diameter of a log at exactly half its length) in centimetres
L = length in metres

Or in a simpler form:

V = Dm² * L * 0.00007854

V = volume in cubic metres (m³)
Dm = mid-diameter (diameter of a log at exactly half its length) in centimetres
L = length in metres
0.00007854 = π ÷ 40000