Black Hole Radius Calculator

Calculate the Schwarzschild radius (event horizon) of a black hole based on its mass

Input Parameters

1 solar mass = 1.989 × 10^30 kg

Calculation Results

Calculation Formula

Schwarzschild Radius (Rs) = (2 × G × M) / (c²)

Where:
Rs = Schwarzschild radius
G = Gravitational constant (6.674 × 10-11 m³/kg/s²)
M = Mass of the black hole
c = Speed of light in vacuum (3.0 × 10⁸ m/s)

Result

Schwarzschild Radius:

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Result in Different Units

Meters (m)

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Kilometers (km)

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Black Hole Radius Calculator Usage Guide

Learn how to use the Black Hole Radius Calculator and understand the physics behind it

How to Use This Calculator

  1. Enter the mass of the black hole in solar masses. One solar mass is approximately the mass of our Sun (1.989 × 10³⁰ kg).
  2. Check the "Convert to kilograms" box if you prefer to input the mass directly in kilograms.
  3. Click the "Calculate" button to compute the Schwarzschild radius.
  4. The calculator will display the radius in both meters and kilometers, along with the formula used for the calculation.

Understanding the Schwarzschild Radius

The Schwarzschild radius is the radius of the event horizon of a non-rotating black hole. It represents the boundary beyond which nothing, not even light, can escape the gravitational pull of the black hole.

For example, if you were to compress the entire mass of our Sun into a sphere with this radius, it would form a black hole. The Schwarzschild radius for the Sun is approximately 2.95 km.

Interesting Facts

  • The radius of a black hole increases as its mass increases. For instance, a black hole with 10 solar masses would have an event horizon about 29.5 km across.
  • The supermassive black hole at the center of our Milky Way galaxy (Sagittarius A*) has a mass of about 4 million solar masses, giving it an event horizon about 12 million km across.
  • For comparison, Earth's mass is about 3 × 10⁻⁶ solar masses, resulting in a Schwarzschild radius of about 9 × 10⁻³⁴ meters - far smaller than an atom.