Can active coils include a fraction?

Yes. Active turns need not be whole numbers. Use the drawing value rather than rounding to an integer.

Should I always subtract two from total coils?

No. End treatment changes the active count. Enter active coils established for the actual spring design.

Does the default modulus fit every steel?

No. The default is illustrative; enter the material value for the specified alloy and operating temperature.

Can I use this rate to approve a working load?

No. Rate alone does not establish allowable travel, stress, stability or fatigue life. Check the complete spring design.

Precision Springs, Stampings & Micro-Formed Components calculator

Compression Spring Rate Calculator

Estimate the nominal stiffness of a round-wire helical compression spring. Use mean coil diameter, wire diameter, active coils and the material shear modulus.

What this calculator does

Estimate nominal elastic stiffness of a constant-diameter round-wire compression spring from its geometry and material modulus.

Formula used

Shear modulus in N/mm² = shear modulus in GPa × 1000
Spring rate = shear modulus × wire diameter^4 ÷ (8 × active coils × mean diameter^3)
Spring index = mean coil diameter ÷ wire diameter

Inputs explained

Wire Diameter: Measured round wire diameter before any coating allowance.
Mean Coil Diameter: Outside coil diameter minus one wire diameter.
Active Coil Count: Coils free to deflect, from the drawing or qualified design.
Material Shear Modulus: Torsional modulus for the specified alloy at operating temperature.

How to use the result

Best suited to nominal spring stiffness comparison, wire diameter sensitivity review.
Excludes variable pitch, conical springs, end effects and contact between active coils. Does not verify stress, buckling, fatigue or working travel.

Current U.S. benchmarks

The producer price index for steel mill products stands at 381.162 (BLS, Aug 2026), up 23.4% from a year earlier. Quotes priced off last quarter's material cost miss this move.
The U.S. has 53,790 fabricated metal products establishments employing about 1,441,471 workers (Census County Business Patterns, 2023).

Common questions

Can active coils include a fraction? Yes. Active turns need not be whole numbers. Use the drawing value rather than rounding to an integer.
Should I always subtract two from total coils? No. End treatment changes the active count. Enter active coils established for the actual spring design.
Does the default modulus fit every steel? No. The default is illustrative; enter the material value for the specified alloy and operating temperature.
Can I use this rate to approve a working load? No. Rate alone does not establish allowable travel, stress, stability or fatigue life. Check the complete spring design.

Last reviewed 2026-10-12.