AmesWeb

Compression Spring Calculator

Use this compression spring calculator to size a helical compression spring from known dimensions, a target spring rate, or measured load-and-height data. It is written for both general users who want clear answers and engineers who want the main design checks on one page.

The calculator reports spring rate, active and total coils, solid height, maximum load at solid, corrected shear stress, factor of safety, spring index, and an optional buckling check. Fatigue life and natural-frequency checks stay on separate pages because they answer different design questions.

1. Choose design mode
Choose the design mode first. Then fill in only the active fields shown below.
Quick start
For general usersFor engineers
  • Use Dimensional when you know free length and coil count.
  • Use Rate based when you know free length and target spring rate.
  • Use One load + free length or Two loads when you have measured test data.
  • Only fill in the fields that are active for the selected mode. Inactive fields are ignored.
2. Geometry, load data, and material
Compression spring terminology
Always required.
Enter the spring diameter value that matches the diameter type you selected.
Select whether your input is outside diameter, mean diameter, or inside diameter.
Used when free length is known.
Used in dimensional mode.
Use active coils if you know working coils; use total coils if you know the full coil count.
Used when the target spring rate is known.
End type affects total coils, solid height, and pitch.
Used by load-based modes.
Used by load-based modes.
Used only by two-load mode.
Used only by two-load mode.
Predefined materials fill in typical modulus and strength data automatically.
Editable only for user-defined material.
Used only for user-defined material.
Editable only for user-defined material.
3. Units, safety settings, and design checks
Only used when material = User defined.
Used to estimate allowable torsional stress at solid height.
Compares required design factor with calculated factor of safety.
Checks slender springs for possible buckling using the selected end condition.
0.5 fixed-flat ends, 0.707 fixed/pivoted, 1 both pivoted, 2 one end free.
The spring is reported stable when the calculated buckling factor is at least this value.
Use Wahl-corrected stress for ordinary springs. Use the preset option only when the spring has been intentionally preset or set removed.
Start with the default values and click Calculate. Results appear only after a valid calculation.
How this page works

For general users: enter the values you already know and let the calculator solve the rest. The results section explains whether the design looks reasonable and whether basic checks pass.

For engineers: the page keeps the same main static-sizing logic as the older dimensional/rate-based and load-based calculators. It reports geometry, stiffness, solid-height loading, stress, factor of safety, and an optional buckling check.

Main symbols

  • d = wire diameter
  • D = mean coil diameter
  • Na = active coils
  • Lf = free length
  • Ls = solid height
  • C = spring index = D/d

Core equations

k = d⁴G / (8D³Nₐ)
C = D / d
Kw = (4C − 1)/(4C − 4) + 0.615/C
τ = K · 8FD / (πd³)

Design checks

Buckling ratio = ((πD/α) · √(2(E−G)/(2G+E))) / Lf

Use the Wahl factor for ordinary unpreset springs. Use the curvature-only stress option only when the spring has been intentionally preset or set removed.

A separate formulas page is still useful for full equation lists and reference tables, but the main equations are repeated here so this page can stand on its own for search users and design work.

Useful definitions
Solid height

The spring length when all coils close up. This is where the maximum solid-load stress occurs.

Spring rate

The change in load divided by the change in deflection. A higher spring rate means a stiffer spring.

Spring index

The ratio of mean diameter to wire diameter. Many practical designs fall roughly between 4 and 12.

Buckling

A long slender spring can bend sideways under compression. The buckling check helps flag that risk.

Frequently asked questions

What can this calculator solve?

It can size a compression spring from dimensions, from a target spring rate, or from one or two load-height conditions.

Why keep fatigue and natural-frequency tools separate?

Those pages answer different engineering questions. Use the fatigue page for cyclic loading and life checks. Use the natural-frequency page when vibration or resonance may matter.

What spring index is usually preferred?

A practical spring index is often kept around 4 to 12. This page shows a warning when the result falls outside that common working range.

Which supporting pages should this page link to?