Schwarzschild Radius Calculator
Calculate the event horizon radius of a black hole from its mass.
This tool is for informational and educational purposes only. It is not a substitute for professional financial, medical, legal, or engineering advice. See Terms of Service.
Can't find what you need?
Request a ToolHow to Use the Schwarzschild Radius Calculator
Enter the mass of the object in kilograms. The calculator computes the Schwarzschild radius, the distance from the center at which the escape velocity equals the speed of light.
- Enter mass. For the Sun, use 1.989 x 10^30 kg.
- Read the result. The radius appears in meters.
- Interpret. If the object were compressed within this radius, it would form a black hole.
About the Schwarzschild Radius Calculator
The Schwarzschild radius defines the boundary of a non-rotating black hole, known as the event horizon. Any object compressed within its Schwarzschild radius becomes a black hole from which nothing, not even light, can escape. The Sun's Schwarzschild radius is about 2.95 km. Earth's is about 8.87 mm. The formula r_s = 2GM/c2 was derived by Karl Schwarzschild in 1916, shortly after Einstein published general relativity.
Frequently Asked Questions
What is the Schwarzschild radius of the Sun?
The Sun's Schwarzschild radius is approximately 2,953 meters (about 2.95 km). The Sun is not a black hole because its actual radius (696,000 km) is far larger.
What happens at the Schwarzschild radius?
At the Schwarzschild radius, the escape velocity equals the speed of light. Inside this boundary (the event horizon), nothing can escape the gravitational pull.
Can any object have a Schwarzschild radius?
Yes, every mass has a theoretical Schwarzschild radius. However, only objects dense enough to fit within that radius actually become black holes.