Thick Wall Cylinder Hoop Stress Formula

Equation for calculate thick wall cylinder hoop stress is,

Hoop Stress = [((i_p x i_r²) - (e_p x e_r²)/ (e_r²) - (i_r²)) ]-[ (i_r² x e_r² x (e_p - i_p)) / (r² x (e_r² - i_r²))]

Where,
i_p = Internal Pressure
e_p = External Pressure
i_r = Internal Radius
e_r = External Radius
r = Radius to Point in Tube