# How much force would your fist need to strike with to punch through a human body?

Okay so, this is kind of a disgusting question... sorry about that in advance, guys. Say you are super strong, super fast, and super durable. There is a not so strong, fast, or durable normal human standing within punching range, and you are a murderous sort and want to punch them. But not just punch them, your goal is to punch through them and connect your fist with their spine (aka put your fist nearly all the way through their body. Gross.)

Let's say this normal human is a male of around average height, weight, and build. You are about 6 ft tall with what appears a healthy human physique (aka you may look muscular, but not appear extraordinarily fat). In actuality, though, you are denser and may weigh up to twice as much as an average human of your height and build (I suppose I am saying you may possess up to twice the mass?)

If I understand this correctly, how hard a punch hits is determined by your fist's momentum, or the combination between mass and velocity. So my question is: What acceleration would you need to achieve during your attack in order to impart enough force to punch your fist into a human body? What happens to you if you do this? (By this I don't mean injury, as I've stated you are extremely durable. I am asking if punching with this much force would throw you off your feet/balance, etc.)

If it's necessary, you can be wearing heavy armor on your arm and/or body to increase your overall weight; you are strong enough it won't slow you down.

• What exactly is the world building context here? Questions about 100% non-fictional things are completely fine here if you could establish how that information is used in your world. Mar 30, 2019 at 8:30
• @Raditz_35 For my supersoldier fluff I'm actually really interested in how much force this would need to be so I can estimate if I can make references to this for attempts at rule of cool without having to go overboard. Mar 30, 2019 at 8:38
• @Demigan Same! I'm working on the design for an alien species that is extremely fast and strong. I have been trying to determine what observable capabilities (like punching a hole in someone) require what degree of enhancement over humans. If I know how hard they need to hit someone, I can go back and figure out the extent of the "power-up" they'd need in order to be able to produce this amount of force, and whether it is within the bounds of reality-stretching I'm prepared to accept. Mar 30, 2019 at 8:42
• @StephenG I thought I stated that for this scenario the aggressor looks human. My aliens are shape-shifty, so while they retain some of their original properties (like strength, durability, and overall mass) they can look like an average human Joe if they want to. This is why I didn't bother stating it was an alien in the original post, just a person with certain listed properties. Mar 30, 2019 at 9:47
• It occurred to me, based on your comments, that there is really no reason a "punch" needs to be limited to the classic curled fist we usually think of, since I believe the reason we do this is to not break our fingers. If you were durable enough, I suppose you could strike with your hand held out flat, which would make the surface area on immediate impact much smaller, limited to the tips of your ring, middle, and index fingers as the first part of your hand to make contact. Mar 31, 2019 at 6:27

You can get really complicated about this, but if we're really keeping in the spirit of the question you're asking, the answer is that "you can't punch someone hard enough to put a hole in them." Not unless the Puncher and the Punchee are made out of Different Stuff.

The problem is that a fist and a chest (for example) have roughly the same density and the same structural integrity, more or less, so something that's made out of the same kind of materials as a human body is a: isn't physically CAPABLE of moving a fist that fast; b: if they could, the fist and the arm would take almost as much damage as the person getting punched would; and c: the punchee would be getting pushed backward by the blow, dissipating the force more rapidly than you can open up a hole through to their spine.

Now, if your Punching hand is significantly harder and/or denser than a normal human body, then it doesn't have to move very fast at all in order to be able to go through someone. this is really the answer to your question tbh. If you want to punch a hole in someone with some science behind it, your puncher has to be punching with something a lot harder and stronger than what a human is made out of.

• It's actually stated in the question that the puncher is twice as dense as the punched. Also that the puncher may be wearing armor on their hand and arm. You can probably safely assume the question is "How much force is needed to ram a blunt steel object through a human body?" Which might already be information that's available on the internet to be honest... Apr 1, 2019 at 21:07
• @Muuski alas, if it is, I haven't been able to find it :( Apr 2, 2019 at 0:57
• @MarielS what you want to be looking for is news stories about people being accidentally impaled on fenceposts and so forth. I found quite a few yesterday. It actually doesn't take that much to push a piece of iron or steel through a human body. Apr 2, 2019 at 13:09
• @MarielS I don't blame you, I don't know where to find that information either or else I would've posted it. What you might also be able to find is people tearing apart movie physics, like the scene in Indiana Jones where the guy puts his hand into people's chests. But I think medical stories like Morris suggests are probably your best bet. Apr 2, 2019 at 16:07

Im not sure if it would be possible but, in order to give this punch the best possible chance of punching through someone, here are some things to consider.

Firstly, you will want your ‘target’ to be braced against something hard. The reason being is that, as you punched them, they would move and absorb a lot of the force. However, if they are braced against the floor or a tree trunk or a concrete wall, they arent going to move backwards as much, reducing the forces they can absorb. I will assume they are against the floor so that way, gravity is working with you, not against you.

Next, we have to pick where about we are going to hit. This is pretty simple as we are trying to punch through to the spine so we know it is the front of the torso. Your best bet is likely through the lower half of the torso, if you aimed for the upper half, you’d need to also break through the rib cage.

Now, you’d need to overcome the shearing strength of human skin and muscle (though i can’t find any source that tells you what this could be) but, assuming you could apply enough PSI to an area the size of a human fist (roughly 0.45 meters squared in this case) you might be able to do it. For the best effect, i would suggest your humanoid jumps and lands on the target’s soft tissue fist first, applying all of their bodyweight behind the target which is backed against a solid concrete floor.

Alternatively, if you’re just trying to punch someone in their spine by punching through them, that would require a lot less force than punching a hole clean through them.

A quick ballpark

I found one source that states the average shear strength for flesh is about 0.4 MPa or 60 psi. Seems somewhat reasonable based on the known danger of compressed air.

Looking at my fist, I guess the area at about 8 sq inches. The means your punch would have to be about 480 lbs force - sustained through the punching depth from front to spine of about 8 inches.

In reality, punching a person this hard would not be enough because the shear strength will be offset by compression of the targets flesh and momentum transfer. At a guess, I figure 1000 or even 2000 pounds of force is more realistic - but quite possibly not very accurate. I'll assume 1500 pounds.

Force says nothing about speed, and in reality shear strength varies with speed (slow speeds gives more time for material to tear). These question then becomes how do expect to have 1500 pounds of force at the end of your punch.

If you can supply 1500 pounds force continuously during a punch, you won't have to slow down during penetration, otherwise you need to be fast enough that that kinetic energy carries you through the punch as you can't supply enough force to maintain penetration based on continuous muscle force.

This answer assumes the super strong person has material properties much stronger than the target, otherwise you have to compensate for the compression, etc. of the arm delivering the blow.

### Their fist would be going as fast as a bullet.

Your question is about how you'd go about hitting someone's fast enough that the thing you're hitting them with is able to punch a hole clean through their body.

Fortunately, we have these in real life: they're called "bullets". A bullet is simply a small, dense mass that moves at a high enough velocity that it will punch a hole clean through the body of a human it strikes. There are a number of images on the Internet of the damage that a bullet can cause, using ballistic gel as a proxy for human flesh.

So, in order for your murderous superhuman to punch a hole through a human body, their fist will need to go approximately as fast as a bullet.