Spring Design Calculator

Inputs

Target load (F)

Required spring force at the working deflection.

Working deflection (x)

Travel from free length to the working load point.

Mean coil diameter (D)

Mean coil diameter. Outside diameter will be D + wire diameter.

Target spring index (C)

Spring index C = D/d. Values around 6-10 are a common starting point.

Free length (L0)

Unloaded spring length used for solid-height and travel checks.

Material

Sets shear modulus and allowable stress.

End type

Sets inactive end coils and solid height.

Default result

Wire diameter(d)

2.5mm

Pass

Also computed

Active coils(Na)9.68

Approx. total coils(Nt)11.68

Spring rate(k)5N/mm

Corrected shear stress(tau)193MPa

Below allowable static stress.

Allowable shear stress871.2MPa

Spring index(C)8

Method notes 3 notes

This is a first-pass geometry design. It chooses wire diameter from your target spring index, then solves active coils from the rate equation.
Round wire diameters and coil counts to purchasable/manufacturable values, then re-check the rounded design with the compression spring calculator.
Fatigue, set removal, surge frequency, tolerances and end grinding allowance are not modeled.