Radius of Gyration Calculator
r = √(I/A) — the column designer's favourite section property.
r asks: how far from the axis does the area EFFECTIVELY sit? Tubes maximize it; that's why they make the best columns. Always check the WEAK axis r.
Formula
Radius of Gyration Calculator is a free radius of gyration for structural engineers, fabricators and site engineers — instant, accurate and 100% client-side, with the governing formula and reference shown next to the result so the number can be defended, not just quoted.
About Radius of Gyration Calculator
r = √(I/A) — the column designer's favourite section property. The calculation implements r = √(I/A) (Column theory — any steel design text). r asks: how far from the axis does the area EFFECTIVELY sit? Tubes maximize it; that's why they make the best columns. Always check the WEAK axis r.
How to use Radius of Gyration Calculator
- 1Enter Moment of inertia I in cm⁴.
- 2Enter Area A in cm².
- 3Read Radius of gyration instantly — no submit button needed.
- 4Need US units? Flip the SI/Imperial toggle and every field converts.
Why use Radius of Gyration Calculator?
- ✓Implements the standard formula — r = √(I/A)
- ✓Reference cited on-page: Column theory — any steel design text
- ✓One-click SI ⇄ Imperial toggle — values convert in place, physics stays in SI
- ✓Live worked example: the substitution recomputes from your numbers
- ✓Runs entirely in your browser — nothing uploaded, free forever
Frequently asked questions
What formula does the Radius of Gyration Calculator use?+
It computes r = √(I/A), per Column theory — any steel design text. The formula is displayed under the result along with a worked example substituted with your own inputs.
What should I keep in mind when using this calculator?+
r asks: how far from the axis does the area EFFECTIVELY sit? Tubes maximize it; that's why they make the best columns. Always check the WEAK axis r.
Can I use this for real structural design?+
It implements the exact textbook/code formula cited below the result and is ideal for sizing, checking and learning. Final designs should be verified by a qualified engineer against the full code with all load cases.
Is the Radius of Gyration Calculator free to use?+
Yes — completely free, no sign-up, no limits. It runs client-side in your browser, so inputs stay private and results are instant even on slow connections.
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