Calculate Schwarzschild radius, Hawking temperature, photon sphere, ISCO, evaporation time, and time dilation for any black hole mass.
The **Black Hole Calculator** computes the fundamental properties of a Schwarzschild (non-rotating) black hole from its mass. Enter the mass in solar masses, Earth masses, or kilograms, and instantly obtain the Schwarzschild radius, Hawking temperature, photon sphere, innermost stable circular orbit (ISCO), surface gravity, evaporation time, Hawking luminosity, and gravitational time dilation at an observer distance.
Black holes are among the most extreme objects in the universe. The event horizon — the boundary beyond which nothing escapes — scales linearly with mass. Hawking radiation temperature, however, is inversely proportional to mass, meaning small black holes are incredibly hot while supermassive ones are colder than the cosmic microwave background.
Use the built-in presets for real black holes like Sagittarius A* and M87*, or explore hypothetical Earth-mass and primordial black holes. The reference tables reveal how properties scale with mass and how time dilation varies with distance. It keeps the horizon, orbital radii, and evaporation estimates together so the size and thermodynamic behavior can be compared in the same view.
Use this page to connect black hole mass to horizon size, orbital structure, Hawking temperature, and evaporation time without manually carrying the constants through each relation. It is useful whenever you want a non-rotating baseline before comparing different masses or moving on to a more detailed relativistic model. That makes it a compact reference for the most common Schwarzschild relationships.
Schwarzschild Radius: Rs = 2GM/c² Hawking Temperature: T = ℏc³ / (8π²GMk_B) Photon Sphere: r_ph = 1.5 Rs ISCO: r_ISCO = 3 Rs (Schwarzschild) Evaporation Time: t ≈ 5120π G²M³ / (ℏc⁴) Time Dilation: √(1 − Rs/r) at distance r
Result: Rs ≈ 29.5 km, T_H ≈ 6.17×10⁻⁹ K, evaporation ≈ 2×10⁶⁷ years
A 10 solar-mass stellar black hole has a Schwarzschild radius of about 29.5 km. Its Hawking temperature is far below the CMB, so it absorbs radiation much faster than it emits.
The Schwarzschild radius grows linearly with mass, which is why supermassive black holes can have event horizons larger than planetary orbits. Hawking temperature scales the opposite way, so smaller black holes are hotter while large astrophysical black holes are effectively cold on cosmological background scales.
The photon sphere, ISCO, and event horizon are different radii with different meanings. The photon sphere is where light can orbit unstably, the ISCO marks the inner edge of stable circular motion for test particles, and the horizon is the true point of no return. Keeping those radii distinct prevents a lot of common confusion.
These outputs assume a Schwarzschild black hole with no spin or charge. Real astrophysical black holes are expected to rotate, which changes the ISCO, frame dragging, and horizon geometry. Use these results as the non-rotating baseline before moving to Kerr-specific formulas.
It is the radius of the event horizon for a non-rotating black hole. Outside that radius escape is possible in principle; inside it, classical escape is not.
Yes. Hawking radiation causes black holes to lose mass, but the evaporation time for stellar and supermassive black holes is incomprehensibly longer than the current age of the universe.
A shell at 1.5 Rs where photons travel in unstable circular orbits. It defines the "shadow" seen in black hole images.
It is the innermost stable circular orbit, the smallest orbit where a test particle can circle without rapidly plunging inward. Inside that radius, stable circular motion is no longer possible for a Schwarzschild black hole.
Rotation shrinks the ISCO on the prograde side and adds an ergosphere. This calculator focuses on Schwarzschild (non-rotating) results.
Yes. Gravitational time dilation is a confirmed prediction of general relativity, measurable even in Earth's gravity field.