Schwarzschild Radius Calculator

Introduction

The Schwarzschild Radius Calculator helps you find the size of a black hole's event horizon. The event horizon is the point where nothing can escape a black hole, not even light. Every object with mass has a Schwarzschild radius - if you squeeze that object small enough to fit inside this radius, it becomes a black hole.

This calculator uses the simple formula Rs = 2GM/c², where G is the gravity constant, M is the mass, and c is the speed of light. You can enter any mass - from tiny particles to giant stars - and find out how small it would need to be to form a black hole. You can also work backwards: enter a radius to find out how much mass would create a black hole that size. For related physics calculations, try our Gravitational Force Calculator to explore gravity between objects, or use the E = mc² Calculator to understand mass-energy equivalence.

The tool shows your results in different units like kilometers, miles, and light-years. It also compares your black hole to known objects like Earth, Jupiter, and the Sun. You can explore preset examples from electrons to supermassive black holes like the one at the center of our galaxy. The calculator also shows extra details like the black hole's temperature, density, and how it compares to famous black holes in space.

How to use our Schwarzschild Radius Calculator

Enter a mass to find the size of its black hole event horizon, or enter a radius to find what mass would create that black hole. The calculator will show you the Schwarzschild radius and many other physics properties.

Mass: Type in the mass of the object you want to turn into a black hole. You can use regular numbers or scientific notation like 1.5e30.

Mass Unit: Pick the unit for your mass from the dropdown menu. Choose from kilograms, tons, pounds, Earth masses, Jupiter masses, or solar masses.

Decimal Places: Set how many decimal places you want in your answer. Enter a number from 0 to 10. For precision in other calculations, check out our Percent Error Calculator to analyze measurement accuracy.

Mass Scale Explorer: Use the slider to quickly explore different mass scales from tiny particles to huge black holes.

Preset Objects: Click any preset button to instantly load the mass of known objects like Earth, the Sun, or famous black holes.

Schwarzschild Radius (Radius Tab): If you switch to the radius tab, enter the event horizon radius to find what mass would create it.

Radius Unit (Radius Tab): Choose the unit for your radius input like meters, kilometers, miles, astronomical units, or light years.

Understanding the Schwarzschild Radius

The Schwarzschild radius is a special distance from the center of an object where gravity becomes so strong that nothing can escape - not even light. This creates what we call a black hole. Named after Karl Schwarzschild who first calculated it in 1916, this radius marks the "point of no return" around a black hole, also known as the event horizon.

How the Schwarzschild Radius Works

Every object with mass has a Schwarzschild radius, but for most things, this radius is tiny. For example, Earth's Schwarzschild radius is only about 9 millimeters - smaller than a marble! The Sun's Schwarzschild radius is about 3 kilometers. To become a black hole, an object must be squeezed down smaller than its Schwarzschild radius. This happens when massive stars die and collapse under their own gravity. Understanding extreme gravitational effects near black holes requires knowledge of both kinetic energy and potential energy at relativistic speeds.

Key Facts About Black Holes

Black holes come in different sizes. Stellar black holes form from dying stars and are typically

Frequently Asked Questions

What happens if I cross the Schwarzschild radius?

Once you cross the Schwarzschild radius (also called the event horizon), you cannot escape the black hole. Even light cannot get out. Time slows down a lot near the edge, and from outside, people would see you freeze at the horizon. Inside, you would fall toward the center very fast.

Can Earth become a black hole?

Earth could only become a black hole if you squeezed it down to about 9 millimeters across - smaller than a marble! This cannot happen naturally. Earth does not have enough mass to collapse into a black hole on its own.

Why do I see infinity for time dilation?

Time dilation becomes infinite right at the event horizon. This means time stops completely at the edge of a black hole when viewed from far away. If you watched someone fall in, they would appear to slow down and freeze at the horizon.

What is the photon sphere shown in results?

The photon sphere is a region where light can orbit the black hole. It sits at 1.5 times the Schwarzschild radius. Light here travels in circles around the black hole. If you were at the photon sphere, you could see the back of your head!

How accurate is the Hawking temperature?

The Hawking temperature calculation is very accurate based on Stephen Hawking's formula. But this temperature is super cold - much colder than space! Bigger black holes are colder. A black hole with the Sun's mass would have a temperature of only 0.00000006 Kelvin.

What do the different black hole types mean?

Black holes are grouped by mass. Stellar-mass black holes (3-100 solar masses) form from dead stars. Intermediate-mass black holes (100-100,000 solar masses) are rare and mysterious. Supermassive black holes (millions to billions of solar masses) sit at galaxy centers. Ultramassive black holes are the biggest known, over 10 billion solar masses.

Why does the calculator show surface gravity?

Surface gravity tells you how strong gravity is at the event horizon. For black holes, this number is huge! The surface gravity gets weaker as black holes get bigger. Strange but true - you would feel less pull at the horizon of a supermassive black hole than a small one.

Can I calculate the Schwarzschild radius for any object?

Yes! Every object with mass has a Schwarzschild radius. You can calculate it for anything - a person, a car, a planet, or a star. Most objects would need to be crushed to impossible tiny sizes to become black holes. Only very massive stars can naturally collapse into black holes.