All of the sites I looked at said "heavy" or "a lot" or "42.3 pounds." Mjolnir was forged from a collapsed star (a white dwarf or a neutron star). This means it is insanely dense.

Worthiness aside, given its size (as seen in the movie) how much should it weigh?

Perhaps I should clarify. Given the average density of a collapsed star, if you took enough material to construct the hammer, how much would that item weigh on Earth?

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    I edited my answer to reflect your update, from the transcript the hammer was forged within the star, not from the star. It is made of a metal called uru, which in the Marvel universe is not attributed to collapsed star material.
    – NominSim
    Commented Jun 21, 2012 at 15:56
  • The Marvel wiki (marvel.wikia.com/Mjolnir) lists Earth-199999 hammer as being forged from the heart of a dying star. I suppose dying could mean collapsing, or about to go super nova. Commented Jun 21, 2012 at 16:03
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    That section is under the film "Issue", but the transcript from the film shows in not from. You forge things in a hot furnace (they seem to have used the sun).
    – NominSim
    Commented Jun 21, 2012 at 16:17
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    The film indicates that it was forged in, not from. Even if it did say from the clear intent is not that the hammer is made of star-matter, but that it was forged by the heat of a dying star, supernova or collapsed. Any difference due to nomenclature is is quite frankly a wording mistake that wasn't meant to be analyzed. If it was made of supernova it wouldn't be solid. If it was made of a collapsed star its very presence would destroy the Earth. If the metal is otherworldly our only clue of its weight is that it can rest on standard ground without piercing it. Commented Jun 21, 2012 at 16:41
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    ALL hammers come from the heart of a dying star - iron is formed when a star has run out of lighter elements to fuse for fuel and the gravitational forces cause heavier elements to come into play. But you're right - it's forged IN, not From. Commented Oct 28, 2012 at 14:32

14 Answers 14


There are two problems answering this question. One - what is the volume? Two - what form of collapsed matter are we talking about? The difference between the density of a white dwarf and neutronium is 7 orders of magnitude (factor of 10,000,000).

So let's assume, for the sake of making it possible to compute a number that the weight of 42.3 pounds was computed for some volume of mostly iron. 42.3lb would be 19.187kg which, would be 2.437l of iron (density is listed as 7.874 g/ml).

2.437l of white dwarf material (approximate density 1,000,000 g/ml) would be 2,437,000kg or about 2,686 US tons.

The Wikipedia article on white dwarfs lists a range of densities for neutronium. We'll use the low end (8.4 e13 g/ml) and this would give 225.6 billion US tons.

Obviously, as was pointed out, the hammer is routinely placed on top of ordinary objects that are not immediately crushed, if the hammer weighed that much. So either:

  1. The hammer was forged of ordinary material and it's weight and/or mass are adjusted in real time by some magic to produce the desired effects.

  2. The hammer really does have a massive weight but it's effective weight and/or mass are adjusted in real time by some magic to produce the desired effects.

The effect is the same, so it really doesn't matter, though one could suppose that the magic to reduce the weight of an object might be simpler than the magic to magnify it (or vice versa). If something like that were true, then my best guess is that Uru is something formed in the heart of a white dwarf and the actual weight is in the neighborhood of 2,000 tons.

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    So, effectively, getting hit with mjolnir would be the same as being hit by 1000 average-sized sedans moving at whatever speed mjolnir is moving at. Commented Aug 9, 2013 at 23:40

The magic of the hammer makes its weight arbitrary. Consider that weight is the force on an object due to gravity, that means that we have to take into account the mass of the hammer and gravity(a constant). However, the hammer doesn't adhere to physics as we know it.

At one moment it can be wielded by Thor, set on a table without breaking the structure, and fly through the air. At the next moment the Hulk himself, who we know to be exceedingly strong can't lift it up. If we attribute these instances to its weight changing, then it can obviously be any arbitrary weight necessary. (Technically we don't know if there is an upper bound but as it's magic it is safe to say there is, in so far as it is convenient to the plot). If we attribute them to some force other than a change in weight, the weight still becomes inconsequential, as it still performs the same way as if it did not have weight.

To reflect on your edit:

From the transcript

Forged in the heart of a dying star, from the sacred metal of Uru...

I think this is saying that the location of where the hammer was forged is in the "heart of a dying star", not that it was forged from the dying star. It is a common idea in a lot of literature to say that an object (sword, spear, shield, hammer) is stronger when forged in a hotter furnace(not being a blacksmith I can't attest to this but it makes sense), I imagine that this is just a matter of Odin indicating that the heat required to forge it came from a dying star.

  • If the material were from a collapsed star, it would move though the ground to the center of the Earth as if it were sinking through water. I remember that the hammer was put or dropped down quite a few times...
    – vsz
    Commented Jun 21, 2012 at 18:07
  • @vsz Actually, if the material were from a collapsed star wouldn't it be dense enough to have its own gravitational field and suck the Earth into itself instead of "falling through the ground"? Good point in this answer about the difference between being "made from" vs. "forged in" a star.
    – Iszi
    Commented Jun 21, 2012 at 21:05
  • @Iszi: Depends on the sort of collapsed star -- a Black hole would pull in the earth, but Neutron star matter would just be amazingly heavy. vsz's description of it sinking through solid earth like it was water is probably appropriate. Commented Jul 9, 2012 at 18:52
  • Were talking about a god forging a weapon beyond the scope of Legendary here.
    – Virusboy
    Commented Feb 3, 2015 at 0:30

Mjolnir, as displayed in the Avengers, would probably weigh 50-60 pounds. We are, for the moment, precluding any magical enchantments that make it unliftable, immovable or able to alter its gravitational constant via the power of the Odin-given worthiness enchantments.

Its head is twice the size of an ordinary sledgehammer (whose head is slightly smaller than the average brick) and weighs about 18-20 pounds. Since it is supposedly comprised of a metal more durable and at least as heavy as iron or steel, we can approximate its unaltered, non-magical specifications.

enter image description here

Thor's hammer is supposed to be a long handled warhammer. As legends have it, during its manufacturer, its handle was somehow reduced in length (likely some trick or machination by Loki) so its head is disproportionate to its handle length. Given Thor's incredible strength that didn't seem to matter much.

Sledgehammers for human use rarely weight more than 10-20 pounds, since generally they are used as tools. To scale one up their normal size to the size of the head of Mjolnir would make its physical weight approximately 50-60 pounds, and make it impossible for an unaltered human being to wield no matter how strong they were!

Even if you were to remove the enchantments for worthiness, its physical weight and very short handle would preclude normal humans from doing much more than picking it up.


With the new request of the hammer being made of collapsed star matter...Astrophysicist Neil Degrasse Tyson says on Twitter:

  • If Thor's hammer is made of neutron-star matter, implied by legend, then it weighs as much as a herd of 300 billion elephants

enter image description here

  • Blah, blah, blah; Let's assume everything said about Mjolnir was true, and not Asgardian hyperbole at best. If it were, just supposing it was, there is no place it could sit on Earth that would be able to support it, effectively.

  • If Mjolnir WAS actually made of collapsed star matter, then there is no where he could set it down that it would not collapse that object (like the helicarrier, for instance) like a tin can. A teaspoon of neutron star can weigh 900 times the mass of the Great Pyramid of Giza! For the record, the Great Pyramid of Giza weighs 5.9 million tons.

  • We can assume it may be more massive than its apparent weight but being truly made of ONLY collapsed stellar matter, even the lightest of such neutronium-like material would cause the hammer to be untenable in any human environment.

  • A neutron star the size of Mjolnir (which is impossible, the smallest neutron star would be the size of the Earth, give or take) would emit a devastating amount of electromagnetic radiation i.e. gamma rays and other assorted deadly EM phenomena. Thor would need completely radiation-proof friends.

  • More importantly, if you could get that much neutron material in a tiny space such as Mjolnir, its gravitational field would cause it to rip the Earth asunder due to the gravitational imbalance between the Earth and the hammer. It wouldn't be pretty.

  • Since we have seen Mjolnir sitting on tables, lying on city streets, Thor standing in office buildings, the hammer sitting someplace in the SHIELD helicarrier without THOR holding it up, we can be safe assuming it is not weighing more than the Great Pyramid of Giza. Or more likely fifty Pyramids of Giza due to neutron star material density...


Marvel produced a trading card which specified Mjolnir's weight as 42.3 lbs. Given its dimensions, it would be considered very light, its physical density would be lighter than aluminum.*

enter image description here

*Excerpt from Matt Shipman's North Carolina State blog interview with materials scientist, Suveen Mathaudhu:

  • Using the dimensions and weight on Marvel's trading card, Mathaudhu estimates that the density of Mjolnir is about 2.13 grams (g) per cubic centimeter (cc). That makes it even lighter than aluminum, which has a density of 2.71 g/cc.
  • But it wasn't made from steel, it was made from collapsed star matter. Commented Jun 21, 2012 at 15:40
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    Not only would it collapse the street and surrounding buildings, but matter would begin to orbit around it. The gravitational pull would be so strong (at such a tiny distance and great mass) that matter hitting it would become one with the hammer, until it had consumed the Earth itself. It would also be invisible, as light wouldn't be able to escape its event horizon. Commented Jun 21, 2012 at 16:45
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    I was trying not to traumatize people with such a horrific vision. Brrrrr.... Commented Jun 21, 2012 at 16:47
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    @Gorchestopher H: A neutron star is not a black hole.. (unless the entire star went into making the hammer, not just a small part of it) Commented Jun 21, 2012 at 17:16
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    @vsz Yes, more. en.wikipedia.org/wiki/Newton%27s_law_of_universal_gravitation A neutron star the size of Mjolnir (which is impossible) would weigh at least half as much as the moon. So, earth would be 22 times more massive than it, but have a radius more than 22 MILLION times greater. Thus the gravitational pull would FAR exceed Earth's own (unless you were standing 5000 miles away from it). It would also shine X-Rays, be approximately 1 Million Kelvin degrees, and, would be an explosion, as its massive gravity still wouldn't be enough to hold its subatomic particles together. Commented Jun 21, 2012 at 18:36

Mjolnir, Thor's hammer, was crafted from uru, an element native only to Thor's realm, Asgard. It being a heavy metal, logistically speaking, I'd say it weighs at least a good 50 pounds or so, but its weight is not the key. Mjolnir, from the day it was begotten had a spell cast on it, by the All-Father Odin, literally the spell from the movie Thor, stating only the worthy may wield the hammer, and the beholder will have the power of Thor.

So staying precise, in truth no one besides Thor himself can lift Mjolnir, no matter its weight.


As I pointed out in my answer here, you're misreading the passage. The blacksmith Eitri and his assistants Brok and Buri used the core of a dying star as the heat source to "forge a mold with which he birthed Mjolnir".

This "heart" (which presumably also served to heat the Uru from which the hammer is constructed) was not inside the star at the time but rather had already been ejected from the star as it exploded or collapsed.

There's an image of them hard at work in Thor Vol 2 #80

enter image description here

Given that Uru is a relatively dense metal, we can assume that the weight of the hammer (sans enchantments) is around a couple of hundred(ish) pounds.


The minimum weight of a neutron star is that of about 1-2 solar masses. This is however all condensed into a sphere of a few hundred kilometres across.

However such a huge sphere needn't all be used in the forging process so only, lets assume, a cubic foot is used. This still constitutes a mass of about 10^12 metric tons. Clearly however this cannot be the case otherwise the the force exerted would be a million times greater than earth's gravity.

Clearly this can't be true, otherwise enemies, friends and buildings would be sucked into the hammer.

So what could it be? Mjolnir was forged from Uru in a dying star. If it was from a star dying 'peacefully' and becoming neutronium, perhaps it was formed in the wake of a supernova?

All elements greater in mass than iron-56 can only be made via supernovas. This leads me to believe that the material is an isotope of Iron. Why Iron? Iron has a rich history of being involved in folk-lore and magic being able resistant to magic but also often enchanted as Uru is also.

As such I'd estimate it weight about twice as much as a standard sledge hammer, having a look at the pictures of it.

  • If you place a one-kilo object one meter away from a 10^11 metric ton (10^14 kilo) object, it will experience a gravitational force of 6700 Newtons, or enough to accelerate it at 6700 m/s^2. Since we do not see small nearby objects accelerating and crashing into the hammer at high speeds, it is safe to say that the effective mass is vastly less than 10^11 metric tons. (Probably less than 10^6, at which point the gravitational effect wouldn't really be noticable.)
    – Rex Kerr
    Commented Jun 21, 2012 at 16:11
  • @RexKerr That's what I said...didn't I? Here's my working.
    – AncientSwordRage
    Commented Jun 21, 2012 at 16:13
  • Sort of. I calculated before reading, I guess! (If you had stated things in terms of gravitational mass vs. inertial mass I would have understood instantly; "weight" can also customarily mean mg which could also give different results than G m1 m2 / r^2, e.g. if the object levitated itself relative to the earth.)
    – Rex Kerr
    Commented Jun 21, 2012 at 16:43
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    Inertial and gravitational mass are the same to within about as many sig figs also. I don't see it any less reasonable that the effective mass for g on the earth would be off but not for other things than that inertial mass would be off. Anyway, I agree about the formal definition of weight. That's why I said "customarily".
    – Rex Kerr
    Commented Jun 21, 2012 at 16:55
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    A neutron star is a dead star, not a dying star. Commented Jun 21, 2012 at 19:35

So here is a pretty good Vsauce video on this.

To summarize - Thor's hammer wasn't made OF a dying star, just IN a dying star. However, if it were made of dying (in this case neutron) star material, it would weigh about 10 quadrillion lbs; given its density and size, anything within 100ft of the hammer would be pulled in at almost the speed of sound, torn apart with gravitational tidal force in the process. If dropped, the hammer would cause an explosion equal to about 1.3 million Tzar-Bomba nukes, killing off a good chunk of humanity, and sinking through the Earth to rest at the Earth's core.


If Mjolnir was forged from a dying star or neutron star, than below is an approximate weight.

5 millilitres of neutron star material has a mass of approximately 5,500,000,000 tons.

The Dimensions of Thors hammer has been estimated at 4x4x8in or having a volume of 128 millilitres.

Mjolnir can have an estimated mass of 140,800,000,000 tons.

  • 1 Earth = 46,875 Mjolnir's
    – Mass
    Commented Aug 25, 2012 at 5:42
  • 1mL is a volume 1cm^3, so your result is off by a factor of 2.54^3 or about 16.4.
    – Niall C.
    Commented Sep 16, 2012 at 20:47
  • The hammer in the recent movie looks quite a bit bigger than 4"x4"x8".
    – Kevin
    Commented Oct 27, 2012 at 14:03
  • @Kevin: I thought so too, but all the sources I could find say it's around 8.5"x4.5"x4.5" or 8.5"x5.5"x5.5". I guess Chris Hemsworth's hands aren't as big as I imagine. Based on my own rough estimate using Chris' head, the 8.5" length for the length of the hammer head sounds about right. Commented Aug 10, 2013 at 1:22
  • Forged "in", not "from"...scifi.stackexchange.com/a/80806/20774
    – Valorum
    Commented Sep 29, 2015 at 21:01

Mjolnir's weight, through the magic applied to it during forging, increases as force is exerted on it. At rest, it is the epitome of the 'immoveable object' and when Thor throws it, it becomes the epitome of the 'unstoppable force'. By legend it is a weapon of no equal in the universe save Odin's spear, Gungnir, which was forged through similar means. You cannot analyze scientifically its properties because it is magic and therefore all rules of science and physics will not apply to it, save what will suit the story plot. No one but Thor can wield it. I'd bet the allfather's magic would cancel out any "strength" or force anything could exert on it, including the Hulk. Because magic only has limits if you imagine limits. Science, on the other hand, which is how the Hulk was created, is finite.


Clealy Mjolnir's weight changes dependent of the situation. It may be light enough to set on a table without crashing through the floor and it can be heavy enough that even the Hulk can't lift it off the hanger deck of the Hellcarrier. In Einstein's theory of general relativity, the effects of gravitation are ascribed to spacetime curvature instead of a force. To match the theory, Mjolnir's enchantment must be able to warp the spacetime curvature around itself. The maximum weight which Mjolnir may obtain is probably unmeasurable but it seems that it only becomes as heavy as it needs to be.


The details of the the dying star are irrelevant. In order to calculate the mass (or weight) of it, you would need to at least know the chemical properties of its metal (Uru). The properties (including its density) are unknown because most samples are "heavily shielded by magic". Density of a metal is determined by its atomic structure.

The dying start is relevant to Mjolnir because of the massive amount of heat required to deform it. Being forged in a dying star would not increase the density of Uru (or the weight of Mjolnir). It might ensure that there are no impurities or bubbles (to ensure pure solid uru) - but the density of Uru would remain the same, be destroyed, or become another element entirely.

Either way, the best we could do to imagine the heaviest possible hammer is use the density of a hammer made of our own heaviest metal (without impurities).

We cannot know anything about the weight of Mjolnor without knowing more about Uru. All we know is that is a highly unmalleable heavy metal. Might be as dense as Lead or Iron for all we know.

Like others have said, the real truth to Mjolnir lies in its magic.


What if the hammer (Mjölnir) is not just a hunk of metal, but rather a concentration of Higgs Bosons with the "hammer" really being a containment device. I base this on the interaction between Captain America's vibranium shield vs Mjölnir.

Since vibranium can absorb (or cancel out?) kinetic energy, and Higgs Boson gives something its mass, ("kinetic energy") then the reaction of those two meeting would be an incredible force indeed.

If it is a Higgs Boson variable containment device, then it would be able to rest on normal object. Maybe people are unable to lift not because it's heavy, but rather it increases the nuclear strong force and the hammer literally becomes nuclearly bonded to whatever surface it's in contact with. Modifying the strong nuclear force would be fairly easy if it's modifying the Higgs field with impunity.

And in order to keep continuity, the Higgs Bosons could have been collected from a dying star, where the increase in mass would allow for easy harvesting of the bosons.


  • This answer also ties in to the line from Thor about science and magic being one and the same in Asgard.
    – Monty129
    Commented Aug 14, 2013 at 20:14
  • Yes, well that's a very, very interesting theory. I have a simpler one: You are not worthy.
    – user20155
    Commented Feb 29, 2016 at 4:37

weight of hammer for anyone that is not Thor

Weight of hammer = max lift capacity of whatever/whoever is trying to lift it + 1

so no matter who is trying to pick it up, it is not possible, except in one of the marvel cartoon movies, Hulk picked it up I believe


It's only logical it was made from a dying star, since if it was not extremely heavy it could not be a planet busting weapon - as it is in the comics.

My explanation is that it is made of a dying star, and Odin's enchantments allow it to weigh only 42 lbs for the wielder but still hit with enough force to bust planets.

Also the weight is controlled by Thor's mind, so when he is holding back he can hit normal people without killing them, but when fighting gods and beings like Galactus he can hit with planetary force.

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