How Much Does a Black Hole Weigh in Pounds?

Black holes range from roughly 6.6 × 10³¹ pounds for the lightest known stellar-mass examples up to around 7.9 × 10⁴¹ pounds for the most massive objects discovered in simulations and distant quasars. That spread covers more than ten orders of magnitude, which is part of what makes the question so interesting. Astronomers express black hole masses in “solar masses” rather than pounds, but translating between the two is straightforward once you know the Sun tips the scales at about 4.4 × 10³⁰ pounds. The real surprise is not any single number but how wildly different black holes can be from one another.

Stellar-Mass Black Holes

The most common black holes are the ones born when massive stars die. These stellar-mass black holes typically weigh between about five and fifty times the mass of our Sun, which puts them in a range of roughly 2.2 × 10³¹ to 2.2 × 10³² pounds. To give that some grounding: the lighter end is about 22 million trillion trillion pounds, a number so large it already defeats everyday intuition. Stars need to start out at about twenty solar masses or more, with substantial helium cores, for their remnants to collapse past the neutron-star limit and become black holes.

Not every massive star ends the same way. Detailed simulations of core-collapse supernovae have identified multiple formation channels. Some involve a failed or “aborted” explosion in a low-metallicity star, leaving behind a black hole of perhaps up to forty solar masses. Others are quieter affairs where roughly five to fifteen solar masses of material simply collapses without a dramatic supernova at all.¹ Stars above about forty solar masses can bypass the explosion phase entirely and collapse directly.²

When researchers model the overall population of stellar-mass black holes across cosmic history, the distribution is relatively flat up to about fifty solar masses and then drops off steeply for heavier ones.³ In pounds, that fifty-solar-mass boundary works out to about 2.2 × 10³² pounds, or 220 million trillion trillion. Above that threshold, stellar-mass black holes become increasingly rare.

Intermediate-Mass Black Holes

Between the stellar-mass population and the monsters at galaxy centers sits a category that has long been difficult to pin down. Intermediate-mass black holes occupy an approximate range of one hundred to one hundred thousand solar masses, translating to roughly 4.4 × 10³² to 4.4 × 10³⁵ pounds.⁴ For years, evidence for their existence was circumstantial. That changed with the detection of a gravitational-wave event called GW190521, consistent with a binary merger producing an object of about 150 solar masses, or around 6.6 × 10³² pounds, providing the first direct evidence that black holes in this intermediate range actually form.

More recently, astronomers studying the giant star cluster Omega Centauri found seven fast-moving stars near its center whose velocities were too high to be explained by the cluster’s ordinary gravity. The speeds required a central dark mass of at least 8,200 solar masses, roughly 3.6 × 10³⁴ pounds, making it one of the strongest local-universe candidates for an intermediate-mass black hole.⁵ Objects like this may represent a missing link between stellar remnants and the supermassive black holes found in galaxy cores.⁶

Supermassive Black Holes

Most large galaxies, including our own, harbor a supermassive black hole at their center. These objects start at around a million solar masses and can reach billions. The Milky Way’s central black hole, Sagittarius A* (Sgr A*), has a mass near four million solar masses, which converts to about 1.76 × 10³⁷ pounds.⁷ That is roughly 17.6 billion trillion trillion pounds, if the word “trillion” repeated twice in a row helps convey the scale (it probably doesn’t, but such is the nature of these numbers).

Sgr A* is modest by supermassive standards. The black hole at the center of the galaxy M87 is far heavier. The Event Horizon Telescope collaboration, which produced the first-ever image of a black hole shadow in 2019, measured M87*’s mass at about 6.5 billion solar masses.⁸ In pounds, that is roughly 2.9 × 10⁴⁰, or 29 trillion trillion trillion. M87*’s mass alone exceeds many small galaxies’ total stellar mass.

Ultramassive Black Holes at the Extreme End

At the absolute top of the scale are so-called ultramassive black holes, objects above about ten billion solar masses. In a large cosmological simulation called ASTRID, the most massive black hole found at a cosmic redshift of two had a mass of about 180 billion solar masses, approaching a theoretical upper limit in the range of 50 billion to 270 billion solar masses.⁹ Converting the 180-billion-solar-mass figure gives roughly 7.9 × 10⁴¹ pounds. The simulation traced this object’s history and found it had grown mainly through gas accretion triggered by galaxy mergers, along with at least two mergers with other black holes that each weighed around 100 million solar masses.

Whether objects this massive exist in the real universe remains an open question. The simulation produced only a handful at these extreme masses. But even more conservative observed candidates, such as the black hole in the galaxy NGC 4889 (estimated at roughly 20 billion solar masses), would weigh in at about 8.8 × 10⁴⁰ pounds. The range from the lightest stellar-mass black holes to these giants spans more than ten orders of magnitude in mass, a factor of over ten billion.

Why “Weight” Gets Complicated

Asking how much a black hole weighs in pounds is a perfectly reasonable question, but it brushes against a distinction that matters once you think about it. Weight is a force: it describes how hard gravity pulls on a mass. Your body has the same mass whether you’re standing on Earth or floating in orbit, but your weight changes because the gravitational pull changes. In everyday life, pounds are treated as a measure of mass (the “pound-mass”), and that is how the numbers above are calculated, by converting solar masses to kilograms and then to pounds.

A black hole sitting in empty space has enormous mass but, in a strict physics sense, has no weight because nothing is pulling it “down.” If you somehow placed a stellar-mass black hole on a fantastically strong surface (an impossible thought experiment, but bear with it), its weight would depend on whatever gravitational field was acting on it. This is mostly a terminological wrinkle rather than a real limitation. When people ask about a black hole’s weight in pounds, they want to know its mass expressed in a familiar unit, and the conversions above deliver exactly that.

How Astronomers Actually Weigh Black Holes

Nobody drops a black hole on a scale. Every mass measurement relies on observing the black hole’s gravitational influence on surrounding matter or spacetime. The methods differ depending on what kind of black hole you’re looking at.

Stellar orbits: For nearby supermassive black holes, astronomers track stars orbiting the center of a galaxy over years or decades. The speeds and shapes of those orbits reveal the enclosed mass. This technique confirmed Sgr A*’s mass by monitoring stars like S1 and S2 as they whipped around the Milky Way’s center at thousands of kilometers per second.¹⁰
Gravitational waves: When two black holes spiral into each other and merge, they emit gravitational waves whose frequency and amplitude encode information about the masses of both objects. Detectors like LIGO and Virgo have measured dozens of such mergers, giving precise masses for stellar-mass and some intermediate-mass black holes.¹¹
Shadow imaging: The Event Horizon Telescope measures the angular size of a black hole’s shadow, the dark silhouette produced by light bending around the event horizon. Combined with a distance estimate, the shadow diameter yields the mass. This was the method used for M87*.⁸
Gravitational microlensing: An isolated black hole drifting through the galaxy can betray its presence when it passes in front of a background star, bending and magnifying the star’s light. The duration and shape of the brightening event reveal the lens’s mass. Future observatories like the Nancy Grace Roman Space Telescope are expected to detect isolated stellar-mass black holes this way.¹²

Each method has its own sources of uncertainty. Gravitational-wave measurements, for instance, can overestimate mass if the merging black holes are embedded in a dense gas environment, because the gas alters the signal in a way that mimics a heavier system.¹³ Shadow imaging depends on knowing the distance to the black hole accurately, and uncertainties in that distance translate directly into uncertainties in mass.¹⁴ None of these tools is perfectly clean, but cross-checking different methods on the same object generally produces consistent results, which is reassuring.

A Quick Reference Table

Because the numbers span such a huge range, it helps to see them side by side. All figures below use the conversion of one solar mass to approximately 4.4 × 10³⁰ pounds.

Lightweight stellar-mass (~5 M☉): ~2.2 × 10³¹ lbs
Heavy stellar-mass (~50 M☉): ~2.2 × 10³² lbs
GW190521 merger product (~150 M☉): ~6.6 × 10³² lbs
Omega Centauri candidate (≥8,200 M☉): ≥3.6 × 10³⁴ lbs
Sagittarius A* (~4 million M☉): ~1.8 × 10³⁷ lbs
M87* (~6.5 billion M☉): ~2.9 × 10⁴⁰ lbs
Most massive in ASTRID sim (~180 billion M☉): ~7.9 × 10⁴¹ lbs

Every step in that list multiplies the mass by factors of tens, hundreds, or thousands. The jump from Sgr A* to M87* alone is a factor of more than 1,600.

How Black Holes Gain Mass Over Time

Black holes are not born at a fixed size and left to drift unchanged. They grow. The two main feeding mechanisms are gas accretion and mergers with other compact objects. In the early universe, conditions in some large, metal-poor galaxies were especially favorable for rapid growth, with dense gas funneling onto seed black holes and frequent galaxy mergers bringing black holes together.¹⁵

Gas accretion is usually the bigger contributor to mass gain. When matter spirals inward through an accretion disk, a fraction of its gravitational energy is radiated away as light, but the rest adds to the black hole’s mass. During active quasar phases, a supermassive black hole can gain millions of solar masses in a cosmologically short time. The ultramassive black holes found in simulations got the majority of their mass this way, with mergers providing a secondary boost.⁹

Mergers add mass more suddenly. When two galaxies collide, their central black holes eventually sink toward each other through dynamical friction and merge. Gravitational-wave observations have already confirmed this process for stellar-mass pairs, and the upcoming LISA space antenna is expected to detect mergers involving much heavier objects. Each merger event bumps the resulting black hole’s mass up by whatever the smaller partner contributed, minus a few percent radiated away as gravitational waves.

Why There May Be a Maximum Mass

It might seem like black holes could grow without limit, but theoretical arguments suggest an upper bound somewhere in the range of 50 billion to 270 billion solar masses. The reasoning involves the physics of accretion: beyond a certain mass, the radiation pressure from infalling gas becomes so intense that it pushes away the very material trying to feed the black hole, effectively choking off further growth. The most extreme object in the ASTRID simulation, at 180 billion solar masses, sits close to this theoretical ceiling.⁹

On the low end, stellar physics sets the floor. A black hole forms only when enough mass collapses into a small enough volume. The lightest stellar-mass black holes observed are around five solar masses, just above the maximum mass for a neutron star (roughly two to two-and-a-half solar masses). Between those two limits sits a so-called “mass gap” where very few compact objects have been found, though gravitational-wave detections have started to populate it. Converting the lower bound, the lightest known black holes weigh in at about 2.2 × 10³¹ pounds.

Putting the Numbers in Perspective

Earth’s mass is about 1.3 × 10²⁵ pounds. The Sun is roughly 4.4 × 10³⁰ pounds. A small stellar-mass black hole at five solar masses is about five Suns crammed into a sphere only about 30 kilometers across. The density implied by that size is staggering, but the density actually drops as black holes get more massive, because the event horizon radius grows linearly with mass while volume grows as the cube. By the time you reach a supermassive black hole like Sgr A*, the average density inside the event horizon is comparable to water. For the ultramassive objects at hundreds of billions of solar masses, the average density inside the event horizon would be far lower than air at sea level. In other words, the most massive black holes are not the densest. They are, in a peculiar sense, some of the most dilute objects in the universe when measured by mass per volume enclosed within the event horizon.

That counterintuitive fact sometimes trips people up. A black hole is not a tiny infinitely dense marble (though its central singularity may be, depending on which theory of quantum gravity turns out to be right). The event horizon, the boundary from which nothing escapes, is simply a surface in space whose size scales with the mass. For the largest black holes, that boundary is vast, enclosing a volume comparable to our entire solar system several times over.

Everyday Comparisons That Fail

People often try to make black hole masses intuitive by comparing them to familiar objects. The trouble is that no everyday comparison survives contact with these numbers. Saying Sgr A* weighs “as much as four million Suns” is accurate but does not really help, because nobody has an intuitive sense of one Sun’s mass either. Saying it weighs 1.76 × 10³⁷ pounds is precise but meaningless to human experience.

Perhaps the most useful framing is relative. The smallest black holes are just a few times heavier than the heaviest individual stars. The Milky Way’s central black hole, while enormous, accounts for a trivial fraction of the galaxy’s total mass, roughly one part in fifteen thousand. And the most massive black holes known are still a small fraction of their host galaxy cluster’s combined mass. Black holes are heavy in absolute terms but live in a universe where galaxies weigh trillions of solar masses and galaxy clusters weigh quadrillions. The numbers only look absurd when you try to express them in units designed for bathroom scales.

1
The Astrophysical Journal. Channels of Stellar-mass Black Hole Formation
2
Berkeley Scientific Journal. Area of Ignorance in Stellar Physics: Stellar Mass Black Hole Distribution; Lowest Initial Progenitor Mass Limit for Black Hole Evolution
3
The Astrophysical Journal. The Black Hole Mass Function Across Cosmic Times. I. Stellar Black Holes and Light Seed Distribution
4
Astronomy & Astrophysics. Search for intermediate-mass black hole binaries in the third observing run of Advanced LIGO and Advanced Virgo
5
Nature. Fast-moving stars around an intermediate-mass black hole in ω Centauri
6
International Journal of Modern Physics D. Observational evidence for intermediate-mass black holes
7
arXiv. Sagittarius A* — The Milky Way Supermassive Black Hole
8
The Astrophysical Journal Letters. First M87 Event Horizon Telescope Results. VI. The Shadow and Mass of the Central Black Hole
9
The Astrophysical Journal Letters. Ultramassive Black Holes Formed by Triple Quasar Mergers at z ∼ 2
10
Oxford Academic. Stellar orbits near Sagittarius A*
11
Scholarly Review Journal. Exploring the Relationships Between Binary Black Hole Parameters and Gravitational-Wave Signal Characteristics
12
The Astronomical Journal. Detecting Isolated Stellar-mass Black Holes with the Roman Telescope
13
The Astrophysical Journal. Fake Massive Black Holes in the Milli-Hertz Gravitational-wave Band
14
The Astrophysical Journal. Observational Limits on Einasto Dark Matter Parameters from Event Horizon Telescope Images of Sgr A* and M87*
15
Annual Review of Astronomy and Astrophysics. The Assembly of the First Massive Black Holes