# Calculate the Angular Radius of Einstein Ring

The calculator calculates the Ring Angular Radius for given values of Constant of Gravitation, Lens Mass, Speed of Light, Distance from Observer to Source and Distance from Observer to Lens.The deformity of the light from the star is called as the Einstein ring. The radius of an Einstein ring is known as the Einstein radius. Its a usual angle for gravitational lensing.

**Formula:**θ

^{2}= (4GM / c

^{2}) * ((d

_{s}-d) / (d

_{s}*d))

**Where,**θ = Ring Angular Radius, G = Constant of Gravitation, M = Lens Mass, c = Speed of Light, d

_{s}= Distance from Observer to Source, d = Distance from Observer to Lens