Calculator inputs
Use specimen geometry or enter the original area directly.
Example data table
| Material | Cross-section | Peak load | Original area | Ultimate strength | Comment |
|---|---|---|---|---|---|
| Mild steel | Round, 12 mm | 68.0 kN | 113.10 mm² | 601.25 MPa | Typical ductile response with strong reserve. |
| Aluminum 6061 | Rectangle, 20 × 4 mm | 24.0 kN | 80.00 mm² | 300.00 MPa | Good strength-to-weight balance for general parts. |
| Brittle polymer | Round, 8 mm | 9.5 kN | 50.27 mm² | 189.00 MPa | Often shows limited elongation before failure. |
| Titanium alloy | Round, 10 mm | 82.0 kN | 78.54 mm² | 1044.06 MPa | Very high strength range for demanding applications. |
Formula used
Original area
Round: A₀ = πd² / 4
Rectangle: A₀ = width × thickness
Hollow round: A₀ = π(OD² − ID²) / 4
Ultimate strength and design checks
σᵤ = Pmax / A₀
σwork = Pwork / A₀
Allowable stress = σᵤ / design factor
Deformation outputs
Engineering strain = ΔL / L₀
Percent elongation = strain × 100
Area change outputs
Reduction in area = (A₀ − Af) / A₀ × 100
Approx necked stress = Pmax / Af
Stress is reported in MPa by treating N/mm² as MPa after unit conversion.
How to use this calculator
- Select the loading mode and specimen cross-section.
- Enter the maximum measured load and choose the load unit.
- Provide geometry values, or override the original area directly.
- Add working load and design factor for service-level checks.
- Optionally enter gauge length, extension, and final area.
- Submit the form to view the result above, then download CSV or PDF if needed.
FAQs
1. What does ultimate strength mean?
Ultimate strength is the highest stress a specimen carries before failure or major instability. It is based on the maximum load divided by the original cross-sectional area.
2. Why does the calculator need original area?
Stress is load per unit area. Without the original area, the tool cannot convert peak load into a meaningful strength value for comparison across materials or specimen sizes.
3. When should I use the area override?
Use it when the test standard already provides the net original area, or when the specimen shape is unusual and a simple round or rectangular formula is not enough.
4. Is ultimate strength the same as yield strength?
No. Yield strength marks the onset of permanent deformation. Ultimate strength is the peak stress reached later in the test, often after yielding in ductile materials.
5. Why is the necked stress labeled approximate?
The calculator uses maximum load with the final area. True fracture stress is usually based on fracture load and final area, so this output is a useful approximation.
6. What does factor of safety show here?
It compares peak load with the entered working load. A larger value means more reserve against the specified service load, assuming the same loading path and specimen behavior.
7. Can I use this for compression or shear?
Yes, as a comparative stress calculator. The mode label helps document the test, but you should still use geometry and standards that match the actual loading case.
8. Which units does the tool support?
It accepts N, kN, MN, and lbf for load. Dimensions support mm, cm, m, and inches. Areas support mm², cm², m², and in².