Formula Used
Inside width: b = B - 2t
Area: A = B² - b²
Second moment of area: I = (B⁴ - b⁴) / 12
Section modulus: S = I / (B / 2)
Bending stress: σ = M / S
Allowable bending stress: σallow = Fy / safety factor
Uniform simply supported moment: M = P × L / 8
Center point simply supported moment: M = P × L / 4
Cantilever end load moment: M = P × L
Euler buckling load: Pcr = π²EI / (KL)²
The calculator uses millimeters, newtons, and megapascals. One MPa equals one N/mm².
How To Use This Calculator
- Enter the outside side width of the square steel tube.
- Enter the wall thickness.
- Add the beam span and the applied transverse load.
- Select the support and load condition.
- Enter yield strength, elastic modulus, and safety factor.
- Add axial compression if the tube also works like a column.
- Press the calculate button.
- Review stress, deflection, allowable load, utilization, and final status.
Example Data Table
| Tube Size |
Wall |
Span |
Load Case |
Load |
Yield Strength |
| 50 mm × 50 mm |
3 mm |
1000 mm |
Simply supported center load |
1000 N |
250 MPa |
| 75 mm × 75 mm |
4 mm |
1500 mm |
Uniform load |
2500 N |
350 MPa |
| 100 mm × 100 mm |
5 mm |
2000 mm |
Cantilever end load |
1200 N |
250 MPa |
Steel Square Tubing Strength Guide
Steel square tubing is used in frames, stands, trailers, brackets, gates, racks, and light structural work. A strength check helps you compare a tube size with the load it must carry. This calculator focuses on bending, shear, deflection, and axial compression. It gives quick engineering style estimates from common beam equations.
What The Calculator Measures
The tool starts with outside width and wall thickness. From those values it finds inside width, metal area, second moment of area, section modulus, and radius of gyration. These section properties describe how the hollow square resists bending and compression. A larger section modulus usually lowers bending stress. A larger moment of inertia usually lowers deflection.
Load And Support Choices
Different support conditions create different moments. A simply supported tube with a center point load has a lower moment than a cantilever with the same end load. Uniform loads spread force over the span. Point loads concentrate force at one location. The calculator lets you compare these cases without changing the whole setup. You can also add an axial load to check combined stress and Euler buckling.
Safety And Interpretation
Steel strength depends on material grade, weld quality, holes, corrosion, temperature, and fabrication details. The yield strength field lets you model common grades or custom steel. The safety factor converts theoretical capacity into a working limit. The deflection limit checks serviceability, not failure. A tube can be strong enough by stress, yet still bend more than desired.
Practical Use Notes
Use consistent units. Enter dimensions in millimeters, forces in newtons, and material stress in megapascals. For unknown steel, choose a conservative yield value. For permanent structures, confirm local codes and use a qualified engineer. This calculator is best for early sizing, comparison, learning, and documentation. It does not replace connection design, weld checks, fatigue review, impact loading, torsion analysis, or official structural approval.
Why Square Tubing Works Well
Square tubing gives strength in two directions. It has flat faces for brackets and welds. Its hollow shape saves weight compared with a solid bar. Good sizing balances capacity, stiffness, cost, and fabrication ease. By reviewing stress, deflection, and safety margins together, you can choose a tube with more confidence during planning.
FAQs
1. What does this steel square tubing calculator estimate?
It estimates section properties, bending stress, shear stress, deflection, allowable load, Euler buckling capacity, and utilization. It is useful for early tube sizing and comparison.
2. Can I use this for welded frames?
You can use it for member checks, but welded frames also need joint, weld, connection, and load path review. Use engineering judgment for final designs.
3. What units should I enter?
Enter dimensions in millimeters, loads in newtons, yield strength in megapascals, and elastic modulus in gigapascals. The calculator converts modulus internally.
4. What is section modulus?
Section modulus shows bending resistance. A larger value usually means lower bending stress for the same moment and better strength against bending failure.
5. What is deflection utilization?
Deflection utilization compares actual deflection with the chosen limit, such as L/360. Values above 100 percent mean the tube bends beyond that limit.
6. Why include a safety factor?
A safety factor reduces theoretical strength to a working limit. It helps cover uncertainty in loads, material quality, workmanship, and service conditions.
7. Does this calculator check buckling?
Yes. It includes Euler buckling for axial compression. It uses elastic modulus, moment of inertia, effective length, and the K factor.
8. Can this replace a structural engineer?
No. It is an estimating tool. Critical structures need code checks, connections, welds, bracing, fatigue, impact, and professional review.