Spring Constant Calculator
Calculate spring stiffness from force and displacement using Hooke’s law k = F ÷ x.
How it works
- 1Enter the applied force and the resulting spring deflection in your preferred units.
- 2The calculator rearranges Hooke’s law (F = k·x) to solve for stiffness: k = F ÷ x in N/m.
- 3Secondary outputs show stiffness in N/mm and lbf/in, plus the elastic energy stored (½·F·x).
Use cases
- Selecting replacement springs by matching the required stiffness to a catalogue N/m rating.
- Verifying a spring’s stiffness by measuring how far a known weight deflects it.
- Estimating elastic energy stored in a compression spring for mechanism design.
Frequently asked questions
What is the spring constant?
The spring constant k (also called spring rate or stiffness) describes how much force a spring exerts per unit of deflection. For example, 50 N applied over 10 mm of deflection gives k = 50 ÷ 0.01 = 5000 N/m = 5 N/mm.
What is Hooke’s law?
Hooke’s law states F = k·x — the restoring force F (N) equals the spring constant k (N/m) multiplied by the displacement x (m). It holds for elastic deformation within the spring’s linear range.
How is elastic energy stored in a spring calculated?
The elastic potential energy is E = ½·k·x² = ½·F·x (since F = k·x). For 50 N over 10 mm: E = 0.5 × 50 × 0.01 = 0.25 J.
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