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Astronomy Calculators

Schwarzschild Radius Calculator

Verified formula Updated Jun 2026 Private — runs on your device

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kg
Verified formula Private

Schwarzschild radius

2.9540

In metres
2,954.0

For general information only — not financial, tax, legal or medical advice. Verify before you rely on it.

How to use the Schwarzschild Radius Calculator

The Schwarzschild Radius Calculator works out your schwarzschild radius, along with 1 related figure in an instant. Enter mass and the result updates as you type — it is free, needs no sign-up, and runs entirely in your browser so your figures stay private.

  1. Enter the mass.
  2. Read off your schwarzschild radius, together with in metres — the calculator updates automatically, with no button to press.

Formula

The Schwarzschild Radius Calculator uses the formula:

Schwarzschild radius = 2 × 0.00000000006674 × Mass ÷ (299792458 ^ 2) ÷ 1000

Worked example

For example, with mass of 1,988,999,999,999,999,901,909,255,192,576 kg, the schwarzschild radius is 2.9540.

Inputs used
Mass 1,988,999,999,999,999,901,909,255,192,576 kg
Results
Schwarzschild radius 2.9540
In metres 2,954.0

Results are estimates for educational use, not professional advice.

Key terms explained

Radius
The distance from the centre of a circle or sphere to its edge.

Frequently asked questions

It is the radius at which an object becomes a black hole — its event horizon. For the Sun's mass it is about 2.95 km.

Use r = 2GM ÷ c², where G is the gravitational constant, M the mass and c the speed of light.

If Earth were compressed to a black hole, its event horizon would be under 1 centimetre across.

Mathematically yes, but an object only becomes a black hole if its mass is actually squeezed within that radius.

Enter the mass. Read off your schwarzschild radius, together with in metres — the calculator updates automatically, with no button to press.

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