Spring Rate Calculator

Spring Calculator Instructions

Attention! Input results shown will be +/- 10% from middle value. Hint: The closer your min and max inputs are, the more accurate your results will be!

Attention! Input results shown will be +/- 10% from middle value. Hint: The closer your min and max inputs are, the more accurate your results will be!

Attention! Input results shown will be +/- 10% from middle value. Hint: The closer your min and max inputs are, the more accurate your results will be!

Definition: Spring rate, also known as spring constant, is the constant amount of force or spring rate of force it takes an extension or compression spring to travel an inch of distance or, in the metric system of measurement, a millimeter of distance. The units of measurement of rate in the English System are, lbf/in (pounds of force per inch) or N/mm (newtons per millimeter) in the Metric System.

Spring rate is the most important part of your compression or extension spring design, but it is also the most complicated spring calculation. You have to take every one of your spring's physical dimensions into account including the material type. Below, you are provided with our free online spring calculator, "Spring Creator", to make your spring calculations a lot easier and faster.

The calculation of spring rate is linear on extension and compression springs; unlike torsion springs where the force is radial. Knowing your spring rate will determine if your spring will function correctly under your working loads. The formulas shown below will explain just how to calculate your compression and extension spring rate.

Formula to Calculate Rate:

D = D outer - d
G = E ÷ 2 ( 1 + V)
k = Gd^4 ÷ (8D^3 na)

Formula symbols:

  • d = Wire Diameter
  • D outer = Outer Diameter
  • D = Mean Diameter
  • E = Young's Modulus of Material
  • G = Shear Modulus of Material
  • L free = Free Length
  • k = Spring Rate (Spring Constant)
  • na = Active Coils
  • v = Poison's Ratio of Material

Formula to Calculate Rate Acquired From Hooke's Law:

k = F ÷ x

Formula Symbols:

  • k = Spring Rate (Spring Constant)
  • F = Force
  • x = Distance Traveled

extension spring and compression spring rate

Design with confidence with Spring Creator 5.0

With Spring Creator 5.0, you have a complete tool at your disposal to create perfect springs for your projects. Design compression, extension, and torsion springs, adjusting every detail to your specifications. Download PDF blueprints and visualize your springs in 3D to ensure they are suitable for your project. Try our tools for free and start designing today!

Created by Alfonso Jaramillo Jr
President Acxess Spring
Over 40 Years of Experience in Spring Engineering and Manufacturing