Spring Force Calculator

Inputs

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Diameter of the spring wire.
mm
Center-to-center across the coil (outside diameter − wire diameter).
mm
Coils that actually deflect (total coils minus the end coils).
Unloaded overall length — used for solid height and the buckling check.
mm
Working compression — used for force and stress at that point.
mm
Sets the shear modulus G and the allowable shear stress.
Sets the inactive end coils and the buckling end-fixity assumption.

Results

Default result
Edit inputs
Force at deflection(F)
12.39N

2.786 lbf

At the deflection entered above.

Also computed

Spring rate(k)1.239N/mm

Spring index(C)Pass10

Corrected shear stress(τ)Pass361.2MPa

Within allowable.

Allowable shear stress995MPa

Static limit at this wire size.

Solid height10mm

Buckling (slenderness L₀/D)Pass4

Stable at any deflection.

Force vs DeflectionThe load line uses the computed spring rate up to travel-to-solid; the operating marker is clamped at the available travel.Force vs Deflection0102030400102030operatingDeflection (mm)Force (N)
The load line uses the computed spring rate up to travel-to-solid; the operating marker is clamped at the available travel.
Method notes 3 notes
  • Static load; ignores fatigue, set and stress relaxation.
  • Allowable shear stress is the static torsional limit at this wire size (45% of estimated tensile strength), before set removal.
  • Buckling assumes the ends are seated between parallel flat surfaces.

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