Drawing No. EH–ME–013 // Mechanical Engineering
Compression Spring Design Calculator
Reviewed August 2026
Check cylindrical helical compression-spring stiffness, deflection, corrected wire stress, solid height and approximate wire-size requirements.
Calculation workflow
Inputs are converted internally to SI, the engineering model is solved, and results are converted back to the selected unit system.
Spring geometry and load
Results
Spring geometry / compression schematic
Worked example
For d = 6 mm, mean diameter 42 mm and eight active coils in steel, the spring index is C = 7.
k = Gd⁴/(8D³Na), so stiffness increases very strongly with wire diameter.
The direct torsional spring stress is multiplied by the Wahl correction factor.
Solid height is approximated as total coils × wire diameter; working compression should retain practical clearance.
Background
The calculator models a cylindrical helical compression spring under axial load.
k = Gd⁴ / (8D³Na)
Mean coil diameter D and active coil count control flexibility. End coils that do not deflect should not be included in Na.
Kw = (4C−1)/(4C−4) + 0.615/C
τ = Kw 8FD / (πd³)
Allowable stress must be supplied from appropriate material/fatigue data for the intended service.
Frequently asked questions
Practical questions about assumptions, limits and interpretation.
The Wahl correction factor accounts approximately for curvature and direct-shear effects that increase maximum wire shear stress in a helical compression spring.
Many practical compression springs use a spring index C = D/d roughly between 4 and 12. Values outside that range can be difficult to manufacture or may introduce unfavorable stress and geometry.
Use material, wire size, heat treatment, fatigue duty, environment and manufacturer or design-standard data. The calculator intentionally asks for allowable stress rather than assuming one value for a material name.
No. Long slender springs can buckle and dynamically loaded springs can surge. These effects require additional geometry, end conditions and frequency checks.