What next?
Stress is one third of a materials check. These are the other two.
How to use this calculator
- Enter the applied force in newtons.
- Enter the cross-sectional area.
- Read the stress in megapascals.
What your result means
Stress is internal force per unit area (σ = F ÷ A), in megapascals — the value you compare against a material’s yield or ultimate strength, staying well below with a safety factor. This is direct axial stress only, not bending or shear.
Why this one is different
Because the cross-section is entered in mm², megapascals fall straight out, and the substituted formula makes that identity visible rather than asking you to take it on faith. A cross-section of zero is refused rather than reported as infinite stress, and a force entered negative is named as compression, since which one it is decides what fails first.
The invisible strain inside every bridge and bone
Stress is force spread through the material itself — the internal push-back that decides whether a beam holds or snaps. Engineers keep working stress safely below the point where a material yields, using a margin called the factor of safety.
It’s the same idea whether you’re sizing a steel column or wondering why a paperclip breaks after enough bends: exceed the limit and structure fails.
How it works
Stress is the internal force per unit area within a material under load. It's the same idea as pressure but inside a solid. Engineers compare it against a material's yield and ultimate strength to check a part won't deform or fail. One newton per square millimetre equals one megapascal.
Formula
Worked example
A steel rod of cross-section 500 mm² carrying 25 kN:
σ = 25,000 N ÷ 0.0005 m²
σ = 50,000,000 Pa
σ = 50 MPa
Typical structural steel yields around 250–355 MPa, so 50 MPa sits comfortably in the elastic region — but a real design check also needs a safety factor.
Frequently asked questions
Is stress the same as pressure?＋
The units are identical (Pa), but stress refers to internal forces in a solid while pressure usually refers to fluids or external loads.
What is yield strength?＋
The stress at which a material starts to deform permanently. Keep working stress safely below it using a factor of safety.
What is the difference between stress and pressure?＋
They share the pascal as a unit but describe different situations. Pressure is a force applied to a surface from outside, usually by a fluid, and acts equally in all directions. Stress is the internal force distribution inside a material resisting a load, and it has a direction — tensile, compressive or shear.
What is the difference between tensile, compressive and shear stress?＋
Tensile pulls apart, compressive pushes together, and shear slides one plane past another. Materials often perform very differently in each: concrete is strong in compression and weak in tension, which is why it is reinforced.
What is the difference between engineering and true stress?＋
Engineering stress divides force by the original area, true stress by the instantaneous area. They diverge once necking begins, which is why a stress-strain curve appears to fall after the ultimate point when the material is still hardening.
What is fatigue and why does it matter?＋
Repeated loading well below yield can still crack a part after enough cycles. Most in-service failures are fatigue failures, which is why cyclic loading is assessed separately from static strength.
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Assumptions & limitations
Engineering formulas are exact; the situations they model are not. Read your result with these limits in mind:
- Gives average direct (axial) stress across the section. Real stress concentrates sharply at holes, notches, welds and sudden changes of section.
- Assumes the load acts through the centroid of the section. An off-centre load adds bending stress on top of this figure.
- Applies to the elastic region only. Past the yield point the material deforms permanently and this relationship no longer holds.
- Includes no safety factor. Design codes apply factors to both loads and material strengths before a section is accepted.