Job postings for FEA roles often list “hand calculations” as a required skill, and I have noticed that this confuses many engineers early in their careers. Some read it as a nostalgic requirement, a leftover from the era before simulation. Others quietly wonder whether they are expected to size aircraft structures with a pencil.
Neither is true. In an FEA role, hand calculations do not mean working without computers. They mean something more important: being able to reason about a structure independently of the software, so that when the software gives you an answer, you know whether to believe it.
After 25 years of building and reviewing FEA models in aerospace, I consider this one of the clearest markers separating engineers who run simulations from engineers who understand them. Here is what the skill actually involves, and how to build it.
Why hand calculations matter in an FEA role
There are four reasons this skill appears in job descriptions, and all four come from real engineering practice rather than tradition.
The first is verification of FEA results. Simple formulas, beam theory being the classic example, let you check a simulation against an independent reference. When the hand calculation and the model disagree by an order of magnitude, one of them is wrong, and finding out which one catches errors in setup or assumptions before they become expensive.
The second is preliminary design estimation. Before any detailed modeling begins, quick hand calculations tell you whether a concept is feasible and shape how you should approach the simulation in the first place. A model built after a rough analytical pass is almost always a better model.
The third is structural behavior insight. Working through calculations by hand builds intuition about load paths, constraints, and material response. That intuition is exactly what you rely on when a simulation produces a result that looks wrong and you need to figure out why. You cannot debug a model using only the model.
The fourth is certification and client trust. In industries like aerospace and automotive, regulatory bodies often require analytical justifications alongside simulation results. A hand calculation is transparent in a way a model is not: anyone can follow it, check it, and challenge it. That transparency builds trust and meets compliance requirements.
The calculations you are expected to know
The expectation is not exotic mathematics. It is fluency with the classical toolkit of structural analysis:
- Axial loading: stress equals force over area
- Bending of beams: Euler-Bernoulli or Timoshenko theory
- Shear and torsion: shear stress in shafts, shear flow in thin-walled sections
- Pressure vessels: hoop and longitudinal stresses
- Buckling of columns: Euler’s critical load
- Vibration: natural frequency of single-degree-of-freedom systems
None of these is advanced on its own. What matters is being able to reach for the right one quickly, apply it with sound assumptions, and know what its simplifications hide.
How to build the skill
If you recognize a gap here, it closes with deliberate practice rather than talent. Four things work.
Start with the right references. Roark’s Formulas for Stress and Strain remains the gold standard for analytical methods. Mechanics of Materials by James Gere covers the foundations, and Shigley’s Mechanical Engineering Design is excellent for machine elements.
Then practice against your own tool. Work through beam problems, pressure vessel shells, joints, lugs, and brackets, and compare your analytical results with simple 1D and 2D FEA models. This comparison is where the real learning happens, because it forces you to explain every discrepancy.
Build a personal handbook as you go. Keep a notebook or PDF of the formulas you use, solved examples, assumptions, and material properties. Over a career, this becomes one of your most valuable tools.
Finally, understand the limitations. Hand calculations rest on simplifications: linear elasticity, ideal constraints, idealized geometry. Knowing when those simplifications break down is as much a part of the skill as the calculations themselves.
The real meaning of the requirement
When a job posting asks for hand calculations, it is asking whether you can independently validate simulation results, estimate mechanical behavior with confidence, and communicate your assumptions and justifications clearly.
It is a sign of maturity, judgment, and engineering integrity. The software will keep getting more powerful. The engineers who stand out will be the ones who never needed it to tell them what to think.
If there is a hand calculation you reach for constantly in your own work, or one you think every FEA engineer should know, I would like to hear it in the comments. This is exactly the kind of skill that improves fastest by comparing notes.
Love the article, Dominique, and definitely on point for new and early practitioners to seriously consider.
I struggle seeing posts online where FEA tool users are struggling to debug very, and in my view unnecessarily, complex models. I don’t see free body diagrams, hand calculations with an initial prediction of the anticipated results, appropriate use of mixed elements (generally just a solid mesh of test or sometimes hex elements), and no use of an incremental complexity approach.
My only addition would be to your list of references. Blevins’ Formulas for Natural Frequency and Mode Shape (the dynamics version of Roark’s) and I always kept a copy of Timoshenko’s Plates and Shells in case I ran across a situation not covered in Roark’s.
Great topic to kick off the new newsletter with. If there is only one lesson I'd like new Engineers to learn and remember, this is it!