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Spring Constant Calculator

Determine spring stiffness from force and deflection, and combine springs in series or parallel.

About Spring Constant Calculator

Stiffness is force per unit deflection. Springs in parallel share the load and add their rates; in series they carry the same load and each deflects, so the combination is softer than the softest one. Series and parallel combination rules for springs are the mechanical mirror of resistors in electrical circuits, but with the roles reversed.

Formula

Spring Constant

k = F ÷ x; parallel springs add, series springs combine as 1/k = 1/k₁ + 1/k₂

k
Stiffness in newtons per metre
series
Springs end to end are softer than either alone

Worked example

With the default values below, Spring Constant Calculator returns Spring Constant of 3,000.00. Change any input above and every figure here is recalculated in your browser.

Inputs used

Force appliedminimum 0 N
120 N
Deflection producedminimum 0 m
0.04 m
Second spring constant for combiningminimum 0 N/m
2,000 N/m

Results

Spring Constant
3,000.00 N/m
Combined Stiffness in Parallel
5,000.00 N/m
Combined Stiffness in Series
1,200.00 N/m
Energy Stored at That Deflection
2.4000 J
Deflection Under Double the Load
0.0800 m

Step by step

  1. 1Values used
  2. 2Spring Constant
  3. 3Spring Constant= 3,000.00 N/m
  4. 4Combined Stiffness in Parallel= 5,000.00 N/m
  5. 5Combined Stiffness in Series= 1,200.00 N/m
  6. 6Energy Stored at That Deflection= 2.4000 J
  7. 7Deflection Under Double the Load= 0.0800 m

Assumptions and limits

  • The result is derived only from the 3 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
  • Figures are rounded for display to 4 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

How is Spring Constant calculated?

k = F ÷ x; parallel springs add, series springs combine as 1/k = 1/k₁ + 1/k₂ Stiffness is force per unit deflection. Springs in parallel share the load and add their rates; in series they carry the same load and each deflects, so the combination is softer than the softest one.

Why does Spring Constant matter?

Series and parallel combination rules for springs are the mechanical mirror of resistors in electrical circuits, but with the roles reversed.

What values do I need to enter?

This calculator takes 3 inputs: Force applied, Deflection produced, Second spring constant for combining. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.

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