Spring Deflection Calculator

Inputs

Wire diameter (d)

Diameter of the spring wire.

Mean coil diameter (D)

Center-to-center across the coil (outside diameter minus wire diameter).

Active coils (Nₐ)

Coils that actually deflect.

Applied force (F)

Load applied to the spring.

Free length (L₀)

Unloaded length, used for travel-to-solid and buckling checks.

Material

Sets shear modulus and allowable stress.

End type

Sets inactive end coils and buckling end-fixity.

Default result

Deflection(x)

10.01mm

Pass

Within available travel.

Also computed

Spring rate(k)1.239N/mm

Spring index(C)10

Corrected shear stress(τ)361.5MPa

Within allowable.

Allowable shear stress995MPa

Travel to solid30mm

Solid height10mm

The curve shows the same spring rate used by the deflection result; the marker is the entered applied force.

Method notes 3 notes

Deflection is calculated from x = F / k after k is found from the spring geometry and material.
Static load only; fatigue, set and relaxation are not included.
Use the stress, travel-to-solid and buckling warnings before treating the deflection as usable travel.