How this calculator works
A linear spring has a restoring force proportional to displacement from equilibrium. Integrating that force gives stored elastic energy. Enter the magnitude of extension or compression. The model applies only within the elastic, approximately linear range; it does not include damping, preload or permanent deformation.
Formula
U = k x^2/2. Solve k = 2U/x^2 or x = sqrt(2U/k).
Worked example
A 500 N/m spring compressed 0.2 m stores 10 J. At 0.4 m it stores 40 J.
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Frequently asked questions
Can compression store energy?
Yes. Both stretching and compression store positive energy in this ideal model.
What happens at zero extension?
Stored energy is zero, but a zero extension cannot determine stiffness from energy.
Does a real spring always follow this?
Only over its linear elastic range. Measure its force curve when the response is nonlinear.