When a closely-coiied helical spring of mean diameter (D) is subjected to an axial load (W), the deflection of the spring (δ) is given by (where d = Diameter of spring wire, n = No. of turns of the spring, and C = Modulus of rigidity for the spring material)

According to Euler's column theory, the crippling load of a column is given by p = π^{2}EI/Cl^{2}. In the Euler's formula, the value of C for a column with both ends fixed is 4.