Extension Spring Rate Constant Calculator and Formula
This spring rate constant calculator will determine any of the values remaining by changing one of the variables then select the "calculate: button for the selected variable.
This calculator will calculate (estimate) the Spring Rate (k) of a extension spring. Spring rate is best determined by test and measurement techniques.
Equation: k = Gd4/8nD3
k = Spirng Constant, pounds of load per inch of deflection
G = modulus of rigidity of spring material, pounds per square inch
d = wire diameter, inches
n = number of active coils, which is the number of coils subjected to flexure (always less than the total number of coils)
D = mean coil diameter, inches = Outer Diameter - Wire Diameter