Mechanical / 07
Spring Rate Calculator
Estimate compression spring rate in N/mm from wire size, mean coil diameter, active coils, and shear modulus.
How it works
k = Gd⁴ / (8D³n)
With G = 79,300 MPa, d = 2 mm, D = 20 mm, and n = 10 active coils, k = 1.98 N/mm.
FAQ
What is the default material?
The default shear modulus is 79,300 MPa for music wire. Use the value appropriate to your material.
Is mean diameter the outside diameter?
No. Mean coil diameter equals outside diameter minus wire diameter.
Which coils are active?
Use coils that deflect under load; end coils may be inactive depending on the end design. The model assumes a close-coiled spring in its linear range.