The Schwarzchild radius calculator is used to determine the potential of a black hole; the formula for the calculator is Rschwarzchild=2MG over C^2. The radius is a way to measure a sphere from which no light, no particles and no information can come from.
When a mass is input into the Schwarzchild radius calculator, it can be determined that the mass will collapse into a black hole when the mass reaches the radius given. For example, if the mass of earth was put into the Schwarzchild calculator, the calculator would then return a number that would be the radius the earth would need to be in order to turn into a black hole. This calculator is the best way for astrophysicists to determine when a planet or a mass of anything will turn into a black hole. When they are able to know the approximate radius of the black hole inevitability, they will be able to estimate the amount of time it will take that mass or object to get to the black hole radius.
In every black hole, there is a radius of light around it. This is called the event horizon and is actually the same size as the Schwarzchild radius. Every black hole has an event horizon and the horizon can be the easiest indicator that there is a black hole present. The event horizon can also be referred to as the photon sphere.