Find Spring Constant k Units Calculator

To find the spring constant k of a spring use the spring constant equation below. The definition of spring constant k: The rate of force required to move the spring 1 inch of distance or in millimeters the rate of force required to move the spring 1 millimeter of distance. Units of spring constant are in either inches, or millimeters. A spring constant unit is then multiplied by the amount of distance traveled by a spring thus giving you your spring force. To calculate spring constant you must know the shear modulus of material, spring wire diameter, outer diameter, number of active coils, and young's modulus of material. Use the spring constant formula on this page or use our spring constant k units calculator below. The equation for spring constant in our spring calculator will help you determine your effective spring constant as well as all of your springs answers.

Spring Constant Units Formula Equation

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

If Spring constant is 1 LBF/inch

it takes 1 lb of force to travel

1 inch of distance

1 LBF/INCH=1LB of force per 1 inch of travel distance


  • G = Shear modulus of material
  • d = Spring wire diameter
  • D = Outer diameter of spring
  • na = number of active coils
  • E = Young's modulus of material
  • V = Poisson's ratio of material