Look up wood pole circumference, diameter, setting depth and class load by species, class and length. We use USDA Rural Utilities Service Bulletin 1724E-150, whose pole tables draw on the minimum dimensions in ANSI O5.1-2008.
These federal table values represent minimum dimensions; use the measured pole dimensions or the pole owner's governing standard for your work.
Ground-line circumference is the distance around the pole where it meets the ground at the tabulated setting depth. Match the species group, class and length to read the minimum circumference in inches.
| Class | Length (ft) | Setting depth (ft) | Southern Yellow Pine and Douglas Fir | Lodgepole and Red Pine | Western Larch | Western Red Cedar |
|---|---|---|---|---|---|---|
| 1 | 35 | 6.0 | 39.0 | 41.5 | 38.0 | 42.5 |
| 1 | 40 | 6.0 | 41.0 | 44.0 | 40.0 | 45.0 |
| 1 | 45 | 6.5 | 42.8 | 45.8 | 41.8 | 47.2 |
| 1 | 50 | 7.0 | 44.6 | 47.5 | 43.6 | 49.0 |
| 1 | 55 | 7.5 | 45.9 | 48.8 | 44.9 | 50.8 |
| 2 | 35 | 6.0 | 36.5 | 38.5 | 35.5 | 40.0 |
| 2 | 40 | 6.0 | 38.5 | 41.0 | 37.5 | 42.5 |
| 2 | 45 | 6.5 | 40.3 | 42.8 | 39.3 | 44.3 |
| 2 | 50 | 7.0 | 41.6 | 44.5 | 40.6 | 46.0 |
| 2 | 55 | 7.5 | 42.9 | 45.8 | 42.0 | 47.8 |
| 3 | 35 | 6.0 | 34.0 | 36.0 | 33.0 | 37.5 |
| 3 | 40 | 6.0 | 36.0 | 38.0 | 35.0 | 39.5 |
| 3 | 45 | 6.5 | 37.3 | 39.8 | 36.8 | 41.3 |
| 3 | 50 | 7.0 | 38.6 | 41.6 | 38.1 | 43.0 |
| 3 | 55 | 7.5 | 40.0 | 42.9 | 39.5 | 44.3 |
| 4 | 35 | 6.0 | 31.5 | 33.5 | 31.0 | 34.5 |
| 4 | 40 | 6.0 | 33.5 | 35.5 | 32.5 | 36.5 |
| 4 | 45 | 6.5 | 34.8 | 36.8 | 33.8 | 38.3 |
| 4 | 50 | 7.0 | 36.1 | 38.6 | 35.2 | 39.6 |
| 4 | 55 | 7.5 | 37.5 | 39.9 | 36.5 | 41.4 |
| 5 | 35 | 6.0 | 29.0 | 31.0 | 28.5 | 32.0 |
| 5 | 40 | 6.0 | 31.0 | 33.0 | 30.0 | 34.0 |
| 5 | 45 | 6.5 | 32.3 | 34.3 | 31.3 | 35.8 |
| 5 | 50 | 7.0 | 33.7 | 35.6 | 32.7 | 37.1 |
| 6 | 35 | 6.0 | 27.0 | 28.5 | 26.5 | 30.0 |
| 6 | 40 | 6.0 | 28.5 | 30.5 | 28.0 | 31.5 |
| 6 | 45 | 6.5 | 29.8 | 31.8 | 28.8 | 32.8 |
Diameter is calculated by dividing circumference by pi. Use the same species group, class and length as in the size chart to find the diameter corresponding to that minimum circumference.
| Class | Length (ft) | Top diameter (in) | Southern Yellow Pine and Douglas Fir | Lodgepole and Red Pine | Western Larch | Western Red Cedar |
|---|---|---|---|---|---|---|
| 1 | 35 | 8.6 | 12.4 | 13.2 | 12.1 | 13.5 |
| 1 | 40 | 8.6 | 13.1 | 14.0 | 12.7 | 14.3 |
| 1 | 45 | 8.6 | 13.6 | 14.6 | 13.3 | 15.0 |
| 1 | 50 | 8.6 | 14.2 | 15.1 | 13.9 | 15.6 |
| 1 | 55 | 8.6 | 14.6 | 15.5 | 14.3 | 16.2 |
| 2 | 35 | 8.0 | 11.6 | 12.3 | 11.3 | 12.7 |
| 2 | 40 | 8.0 | 12.3 | 13.1 | 11.9 | 13.5 |
| 2 | 45 | 8.0 | 12.8 | 13.6 | 12.5 | 14.1 |
| 2 | 50 | 8.0 | 13.2 | 14.2 | 12.9 | 14.6 |
| 2 | 55 | 8.0 | 13.7 | 14.6 | 13.4 | 15.2 |
| 3 | 35 | 7.3 | 10.8 | 11.5 | 10.5 | 11.9 |
| 3 | 40 | 7.3 | 11.5 | 12.1 | 11.1 | 12.6 |
| 3 | 45 | 7.3 | 11.9 | 12.7 | 11.7 | 13.1 |
| 3 | 50 | 7.3 | 12.3 | 13.2 | 12.1 | 13.7 |
| 3 | 55 | 7.3 | 12.7 | 13.7 | 12.6 | 14.1 |
| 4 | 35 | 6.7 | 10.0 | 10.7 | 9.9 | 11.0 |
| 4 | 40 | 6.7 | 10.7 | 11.3 | 10.3 | 11.6 |
| 4 | 45 | 6.7 | 11.1 | 11.7 | 10.8 | 12.2 |
| 4 | 50 | 6.7 | 11.5 | 12.3 | 11.2 | 12.6 |
| 4 | 55 | 6.7 | 11.9 | 12.7 | 11.6 | 13.2 |
| 5 | 35 | 6.0 | 9.2 | 9.9 | 9.1 | 10.2 |
| 5 | 40 | 6.0 | 9.9 | 10.5 | 9.5 | 10.8 |
| 5 | 45 | 6.0 | 10.3 | 10.9 | 10.0 | 11.4 |
| 5 | 50 | 6.0 | 10.7 | 11.3 | 10.4 | 11.8 |
| 6 | 35 | 5.4 | 8.6 | 9.1 | 8.4 | 9.5 |
| 6 | 40 | 5.4 | 9.1 | 9.7 | 8.9 | 10.0 |
| 6 | 45 | 5.4 | 9.5 | 10.1 | 9.2 | 10.4 |
The setting depths tabulated by RUS follow 10 percent of the pole's length plus 2 feet, with a 6-foot minimum. Soil, rock, slope and guying can require greater depth, and the pole owner's construction standard governs.
| Pole length (ft) | Setting depth (ft) | Height above ground (ft) |
|---|---|---|
| 35 | 6.0 | 29.0 |
| 40 | 6.0 | 34.0 |
| 45 | 6.5 | 38.5 |
| 50 | 7.0 | 43.0 |
| 55 | 7.5 | 47.5 |
A pole class defines a horizontal load applied 2 feet from the top, with a lower class number indicating a stronger, thicker pole. Different species and lengths within a class carry about the same load, but their minimum dimensions differ.
| Class | Horizontal load 2 ft from top (lb) | Minimum top circumference (in) | Minimum top diameter (in) |
|---|---|---|---|
| 1 | 4,500 | 27.0 | 8.6 |
| 2 | 3,700 | 25.0 | 8.0 |
| 3 | 3,000 | 23.0 | 7.3 |
| 4 | 2,400 | 21.0 | 6.7 |
| 5 | 1,900 | 19.0 | 6.0 |
| 6 | 1,500 | 17.0 | 5.4 |
We use USDA RUS Bulletin 1724E-150, "Unguyed Distribution Poles--Strength Requirements" (2014), which uses ANSI O5.1-2008 minimum dimensions. RUS Equation 5.2 converts the circumference 6 feet from the butt to the ground-line circumference at the tabulated setting depth; diameter = circumference / pi. Coverage is Classes 1 to 4 at 35 to 55 feet, Class 5 at 35 to 50 feet, and Class 6 at 35 to 45 feet. Species groups are Southern Yellow Pine and Douglas Fir; Lodgepole and Red Pine; Western Larch; and Western Red Cedar. We omit weights because the federal tables do not provide them, and weights vary with species, treatment and moisture.
The charts give minimum pole dimensions and horizontal class loads. Those values alone do not tell you whether a pole can carry wind and ice loads. Use the free Pole Loading Calculator to screen one tangent wood pole for NESC Rule 250B wind and ice load against its capacity by class. The calculator uses the same ANSI O5.1 minimums as these charts.
For a full stamped assessment, use our pole loading analysis service. Make-ready engineering follows that analysis.
RUS tabulates a 6-foot setting depth for a 40-foot pole. The rule takes 10 percent of the pole's length and adds 2 feet, with a 6-foot minimum. Soil, rock, slope and guying can require a deeper setting, and the pole owner's construction standard governs.
Class 4 corresponds to a horizontal load of 2,400 pounds applied 2 feet from the pole's top. Its minimum top circumference is 21.0 inches. Ground-line dimensions depend on species and length. A lower class number indicates a stronger, thicker pole, so class must be read together with those other selections.
Western Red Cedar has a lower designated fiber stress, 6,000 psi, than the 8,000 psi for Southern Yellow Pine and Douglas Fir. To carry about the same class load, it needs a greater ground-line circumference. For a 40-foot Class 4 pole, the listed minimum is 36.5 inches for Western Red Cedar versus 33.5 inches for Southern Yellow Pine and Douglas Fir.
Divide the circumference by pi to obtain diameter in the same units. The chart uses minimum circumferences from the RUS data, with the ground-line value computed using RUS Equation 5.2. Select the species group, class and length first so the circumference corresponds to the pole you are looking up.
These charts provide minimum dimensions and horizontal class loads. The Pole Loading Calculator screens one tangent wood pole for NESC Rule 250B wind and ice load against its capacity by class. We provide the full stamped pole loading analysis as a separate service, followed by make-ready engineering.
We engineer your first 20,000 linear feet through permit approval, free; you pay agency permit fees and any required stamping fee. Active in 24 states. Available across all 50 U.S. states.
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