Huber’s formula calculates the volume of a round log from its middle measurement:
V = L × Amid
where L is the log length and Amid is the cross-section area at the middle of the log. It treats the log as a cylinder whose thickness is the thickness at the halfway point. It is the method most timber traders mean when they say “mid-girth measurement”.
The formula in the form you will actually use
At the yard you measure girth (the tape around the log) or diameter, not area. So:
| You measured | Formula for one log |
|---|---|
| Mid diameter d (m), length L (m) | V = 3.1416 × (d / 2)² × L |
| Mid girth g (m), length L (m) | V = g² × L ÷ 12.566 |
| Mid diameter d (cm), length L (m) | V = d² × L ÷ 12,732 |
All three give cubic metres (CBM). For cubic feet (CFT), multiply the CBM by 35.315.
Worked example 1 — measuring the diameter
A teak log, length 4.00 m, mid diameter 36 cm.
- Convert: 36 cm = 0.36 m; radius = 0.18 m
- Area at the middle: 3.1416 × 0.18² = 0.1018 m²
- Volume: 0.1018 × 4.00 = 0.407 CBM
- In CFT: 0.407 × 35.315 = 14.4 CFT
Worked example 2 — measuring the girth
A log, length 5.00 m, mid girth 160 cm.
- Convert: 160 cm = 1.60 m
- V = 1.60² × 5.00 ÷ 12.566 = 2.56 × 5.00 ÷ 12.566
- Volume = 1.019 CBM (36.0 CFT)
Quick reference: mid-girth to CBM per metre of length
Multiply the figure below by the log length in metres.
| Mid girth (cm) | CBM per metre | Mid diameter (cm) |
|---|---|---|
| 80 | 0.0509 | 25.5 |
| 100 | 0.0796 | 31.8 |
| 120 | 0.1146 | 38.2 |
| 140 | 0.1560 | 44.6 |
| 160 | 0.2037 | 50.9 |
| 180 | 0.2578 | 57.3 |
| 200 | 0.3183 | 63.7 |
Example: a log with 140 cm mid girth and 3.5 m length = 0.1560 × 3.5 = 0.546 CBM.
Huber vs Hoppus vs Smalian vs JAS
| Method | What it measures | Typical result | Where it is used |
|---|---|---|---|
| Huber | Mid girth or mid diameter | True volume of the log | India, Middle East, much of Europe; general trade |
| Hoppus | Quarter girth, squared | About 21.5% less than true volume — it allows for squaring the log | Traditional British method, still common in India and Myanmar teak |
| Smalian | Both ends, averaged | Slightly more than Huber on tapered logs | Forestry and research; good when the middle can’t be reached |
| JAS | Small-end diameter, in a scale table | Conservative — buyer-friendly | Japanese log trade |
The practical point: Huber gives the true solid volume. Hoppus deliberately gives less, because historically the buyer paid for the squared beam, not the round log. Quoting Hoppus volume as if it were CBM is the most expensive misunderstanding in log trading.
Where Huber’s formula goes wrong
- A log that is not round. On an oval or buttressed log, take two diameters at right angles and average them.
- A log with heavy taper. The middle no longer represents the whole log, and Huber under-measures. For badly tapered logs, measure in two sections, or use Smalian.
- Measuring over the bark. Bark is not timber. Deduct the bark thickness twice from the diameter, or measure girth and deduct as per your trade’s practice.
- Rounding too early. Round only the final volume, never the girth or the area.
- Mixing units in one tally. Metres with centimetres, or CBM with CFT, in the same sheet. This is the single most common cause of an argument at reconciliation time.
Doing this for a whole truck, not one log
One log takes a minute. A truckload of 120 logs, measured by hand, copied to paper, then typed into Excel at night, is where mistakes and lost time creep in.
With LumberLinq your staff tally on a phone at the yard — girth and length recorded as measured, volume in CBM and CFT (round logs use the Hoppus convention), working offline and syncing later. If you already tally on paper, photograph the sheet and it reads itself in, row by row, with anything unclear flagged for a person to check before it saves.
See it in 15 minutes or start free — no card needed.
Frequently asked questions
Is Huber’s formula the same as mid-girth measurement? Yes. “Mid girth” is how the trade describes taking the measurement; Huber’s formula is the calculation applied to it.
Why is my Hoppus volume lower than my Huber volume? Because Hoppus uses a quarter of the girth and squares it, which is about 78.5% of the true volume. A 21.5% difference is expected, not an error.
Can I use Huber’s formula for sawn timber? No. Sawn or square timber is simply length × width × thickness. Huber’s formula is for round logs.
What if I can’t reach the middle of the log in a stack? Use Smalian’s formula from the two end diameters, or measure after unloading. Do not guess the middle measurement.
Related: CBM Calculation for Round Logs: Doyle, Scribner, JAS, and Huber Methods Explained · Free timber tally sheet template (printable + Excel)