CHS section properties for the full standard range: area, second moment of area, moduli and radius of gyration. Pick a section and read the values.
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About this CHS Section Properties Calculator
This calculator returns the section properties of any circular hollow section in the standard range, computed from the published outer diameter and wall thickness. Pick a designation and it gives you the area, the second moment of area, the elastic and plastic section moduli and the radius of gyration, along with a scale drawing of the section.
- Structural engineer: pull the properties of a candidate CHS straight into a member check without leaving the calculation or retyping a table row.
- Design engineer: compare several diameters and wall thicknesses quickly during concept sizing, with the section drawn to scale as you change it.
- Checker: verify the properties quoted in a submitted calculation against the section geometry, with every step of the derivation visible.
Every property is computed on the page in visible MathJS rather than read from a stored table, and each one is checked against an independent geometric integration of the same section before it ships. It is an engineering-grade calculator you can audit, duplicate and adapt in CalcTree.
More info on CHS Section Properties
What defines a CHS
A circular hollow section is defined by two published dimensions: the outer diameter and the wall thickness. The inner diameter follows from them, and every property follows from the pair. The library holds those two values exactly as the product standard gives them, so nothing on the page is a tabulated approximation.
How the properties are derived
A CHS is an annulus, so the closed-form geometry is exact. The area is the difference of the two circular areas, the second moment of area is the difference of their fourth-power terms, and the plastic modulus comes from the difference of the two solid sections. Because the section is axisymmetric, the second moment of area, the section moduli and the radius of gyration are the same about every axis through the centroid.
Using the library in your own calculation
The section range is attached to the page as a dataset rather than pasted in as a table, so the same file can be inserted into any other calculation in your workspace. Duplicate the page and the data comes with it, which means a member check you build on top of it stays tied to one copy of the section range rather than a retyped subset of it.
Where the numbers are checked
Each section is verified against an independent numerical integration of the same geometry, carried out by a different method to the closed-form expressions used on the page. Both have to agree to four significant figures for every section in the range.
Common Calculation Errors to Avoid
- Confusing outer and inner diameter: The designation and the properties are both based on the outer diameter. Working from the bore, or from a mean diameter, gives a section that is consistently too small.
- Using plastic properties without classifying the section: The plastic modulus only applies if the cross-section can reach and sustain its plastic moment. Classify the section for the relevant load case first; a Class 3 section is limited to its elastic modulus and a Class 4 section needs effective properties, not the gross ones given here.
- Assuming a CHS cannot be slender: A large diameter with a thin wall can be Class 4 in compression or bending. Check the diameter to thickness ratio against the classification limits before using the gross properties.
- Reading properties from a different standard: Hollow section ranges differ between standards and regions. A designation that looks familiar may have a different wall thickness or a different range of sizes in another standard.
- Treating gross properties as net properties: These are gross section properties. Bolt holes, cope cuts and corrosion allowances all reduce the section, and none of them are accounted for here.
Engineering templates
Common calculators
Design guides
FAQs
Are hot-finished and cold-formed CHS properties the same?
Yes. A circular hollow section has no corner radii, so a hot-finished and a cold-formed CHS of the same outer diameter and wall thickness have identical section properties. That is not true of rectangular and square hollow sections, which have separate libraries here.
Are these the same values as the published section tables?
They are computed from the same published dimensions using the exact geometry of an annulus, which is what the section tables are themselves derived from. Differences in the last digit are rounding in the published tables, not a difference in method.
Why are the properties the same about both axes?
A CHS is axisymmetric, so the second moment of area is identical about every axis through the centroid. That is what makes it efficient as a column and as a member carrying moments in more than one direction.
Can I use this inside my own calculation?
Yes. The section range is a dataset attached to the page, so duplicating the page brings the data with it and you can look up any section from your own maths.
Does it allow for corrosion or holes?
No. The properties are the gross section. Any allowance for corrosion, bolt holes or cope cuts has to be applied separately.
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