LOG
Round Log CFT Calculator (Hoppus Quarter Girth)
How to calculate the CFT of a round log: girth or diameter and length, Hoppus quarter-girth rule or true volume, many logs at once, with rate per CFT.
10.00 cft
Assumptions used EDIT ▾
Leave 0 if the girth is measured under the bark.
Measure the girth with a tape round the middle of the log. Hoppus (quarter girth) is the usual trade rule for logs: it allows for the round log being sawn square, so it gives about 78% of the true volume.
TOTAL VOLUME
10.00cft
Hoppus (quarter girth)
- Cubic metres
- 0.283 m³
How it’s calculated
Hoppus CFT = (girth ÷ 4)² × length ÷ 144 (girth in inches, length in feet)
Example: A log 48 inches round and 10 ft long: (48 ÷ 4)² × 10 ÷ 144 = 10 cft.
Questions
How do I calculate the CFT of a round log?+
Measure the girth round the middle of the log in inches and the length in feet. Divide the girth by 4, square it, multiply by the length and divide by 144.
Why is Hoppus volume less than the true volume?+
Hoppus assumes the round log will be sawn square, so it gives about 78% of the true round volume. Timber is traded on Hoppus in many places.
Estimates for planning, based on the assumptions shown. They are not a guarantee of quantities or professional engineering advice; check critical work with a qualified professional.