JAS – log volume by the Japanese standard

Q: Why is the diameter rounded to an even number?

JAS grades larger logs in 2 cm classes, so a diameter above 14 cm is rounded down to the nearest even number, e.g. 31.8 cm to 30 cm.

Q: Why is an allowance added for long logs?

A long log widens toward the butt. The allowance of (L′ − 4)/2 cm added to the diameter accounts for this taper so long logs are not underestimated.

Q: Is JAS volume larger or smaller than Huber?

It depends on taper. JAS uses the small-end diameter, which lowers the result, but squares it without π – for the same diameter D²·L is 27% more than a cylinder.

The small-end diameter squared method, the standard for logs traded to Japan.

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What is the JAS (Japanese standard)?

JAS (Japanese Agricultural Standard) calculates log volume from the square of the small-end diameter and the length. The diameter is rounded down, above 14 cm to an even number. For logs from 6 m an allowance based on length is added to the diameter to account for taper.

Formula

V = D² · L / 10,000 (L < 6 m) · V = (D + (L′ − 4) / 2)² · L / 10,000 (L ≥ 6 m)

V in m³ · D = smallest small-end diameter in cm, rounded down (above 14 cm to an even number) · L = length in m · L′ = length rounded down to whole meters.

Worked example

A log with a 30 cm small-end diameter and 4 m length: V = 30² · 4 / 10,000 = 0.360 m³. At 8 m: V = (30 + (8 − 4)/2)² · 8 / 10,000 = 32² · 8 / 10,000 = 0.819 m³.

Where it is used

Japan and the log trade to the Japanese market – e.g. exports from New Zealand, the USA, Canada or Russia, where volume is often quoted in “JAS m³”.

Frequently asked questions

Why is the diameter rounded to an even number?

JAS grades larger logs in 2 cm classes, so a diameter above 14 cm is rounded down to the nearest even number, e.g. 31.8 cm to 30 cm.

Why is an allowance added for long logs?

A long log widens toward the butt. The allowance of (L′ − 4)/2 cm added to the diameter accounts for this taper so long logs are not underestimated.

Is JAS volume larger or smaller than Huber?

It depends on taper. JAS uses the small-end diameter, which lowers the result, but squares it without π – for the same diameter D²·L is 27% more than a cylinder.

Other log scaling methods

All 22 methods in the app ›

In your countryDoyle vs Scribner vs International ¼″Three US board foot rules, three different results for the same log. Clearly laid out, in numbers, with the reasons.BF · US · CA In your countrySmalian formulaWhen you cannot reach the middle of the log – on a deck or a truck – you measure both ends.m³ · US · CA In your countryDoyle Log RuleThe oldest log rule still in wide use in the southern and midwestern United States.BF · US In your countryScribner Decimal CA rule built by drawing boards into circles, today the standard for softwood logs in the western United States.BF · US · CA In your countryInternational ¼″ Log RuleIt allows for a ¼-inch kerf, shrinkage and log taper, so it comes closest to the real lumber yield.BF · US Huber formulaThe most widely used scaling method in Central Europe: one diameter at mid-length and the length.m³ · SK · CZ · DE · AT · FR · IE Swedish scaling (toppmätning)Swedish sawmills pay by the small-end diameter: m³to is a cylinder from the top end.m³ · SE Hoppus formulaA traditional British rule still used in the tropical hardwood and teak trade.m³ · GB · IE · IN · GH · MY More methodsSTN 48 0009, ČSN 48 0009, Vermont, Universal (Daniels), Newton, GOST 2708-75, Brereton, Ontario Board Foot, Ontario Cubic, Roy, Alberta, BC Firmwood, Mid-girth, Guo Biao (GB/T 4814)All 22 methods ›