Schwarzschild Radius Calculator
Enter a mass in kilograms or in solar masses to find its Schwarzschild radius, the event horizon at which not even light can escape the resulting black hole.
How to use the Schwarzschild radius calculator
- Choose whether to enter the mass in kilograms or in solar masses.
- Type the mass of the object you want to collapse into a black hole.
- Read the event horizon radius in metres, kilometres and solar radii.
Examples
One solar mass black hole
mass = 1 solar mass (1.989e30 kg)
radius = about 2954 m (2.95 km)
Supermassive black hole
mass = 1,000,000 solar masses
radius = about 2.95e9 m
Frequently asked questions
What is the Schwarzschild radius?
It is the radius of the event horizon of a non-rotating black hole. Compress a mass inside this radius and its escape velocity reaches the speed of light, so nothing can get out.
What is the Schwarzschild radius formula?
r = 2 x G x M / c^2, where G is the gravitational constant, M is the mass and c is the speed of light. The radius is directly proportional to mass.
What is the Schwarzschild radius of the Sun?
About 2954 metres, or roughly 2.95 km. The Sun is far too spread out to be a black hole, but this is the size its horizon would have if it collapsed.
What is the Schwarzschild radius of Earth?
Around 8.9 millimetres. You would have to squeeze Earth's entire mass into a sphere smaller than a marble for it to become a black hole.
Does the formula account for rotation or charge?
No. This is the simple Schwarzschild solution for a static, uncharged black hole. Spinning or charged black holes use the Kerr and Reissner-Nordstrom solutions.
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