Spring Index Calculator

Choose whether the entered coil diameter is mean, outside or inside diameter.

Mean, outside or inside diameter according to the selector above.

mm

Diameter of the spring wire.

mm

Results

Default result
Edit inputs
Spring index(C)
10
Pass

Also computed

Mean coil diameter(D)10mm

Outside diameter(OD)11mm

Inside diameter(ID)Pass9mm

Wahl factor(Kᵥᵥ)1.145

Method notes 3 notes
  • Spring index is C = D / d, mean coil diameter divided by wire diameter.
  • Low C values are hard to manufacture and raise stress concentration; high C values can buckle and tangle more easily.
  • Wahl factor is shown because it is the stress-correction term used by the spring calculators.

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