This square tube section properties calculator finds the area, moment of inertia, and section modulus of a hollow square tube from its outer and inner dimensions. Enter both above.
Formulas (hollow square)
Area A = B² − b² Inertia I = (B⁴ − b⁴) ÷ 12 Section modulus Z = I ÷ (B ÷ 2)
Example
B = 50 mm, b = 40 mm: A = 900 mm², I = 307,500 mm⁴, Z = 12,300 mm³.
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Frequently Asked Questions
How do I find square tube section properties?
Subtract the inner square from the outer for area, and use (B^4 – b^4)/12 for the moment of inertia.
What is section modulus?
It is the moment of inertia divided by the distance to the extreme fiber; it sets the bending strength.
Why use square tube over solid bar?
Hollow tube gives most of the stiffness at a fraction of the weight, since material far from the center matters most.