# How many pounds of pressure does it take to break the average human bone?

**URL:** <https://boards.straightdope.com/t/how-many-pounds-of-pressure-does-it-take-to-break-the-average-human-bone/360914>\
**Category:** Factual Questions\
**Created:** [June 16, 2006, 12:13pm UTC](https://boards.straightdope.com/t/how-many-pounds-of-pressure-does-it-take-to-break-the-average-human-bone/360914 "2006-06-16T12:13:22Z")\
**Posts on this page:** 4\
**Page:** 2

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**Author:** ![robby](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/robby/32/11048_2.png) [@robby](https://boards.straightdope.com/u/robby)\
**Post date:** [June 19, 2006, 3:01am UTC](https://boards.straightdope.com/t/how-many-pounds-of-pressure-does-it-take-to-break-the-average-human-bone/360914/21 "2006-06-19T03:01:48Z")

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> [@Askia](#):
>
> **Dr\_Paprika,** …One last question, though. KN are kiloNewtons, right? How do you convert that to psi?

You don’t.

Kilonewtons (just like newtons) are units of force. Pounds per square inch (psi) are units of pressure.

Isn’t this where I came in? 😉

Or maybe I’m just being whooshed.

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**Author:** ![Askia](https://avatars.discourse-cdn.com/v4/letter/a/96bed5/32.png) [@Askia](https://boards.straightdope.com/u/Askia)\
**Post date:** [June 19, 2006, 7:54am UTC](https://boards.straightdope.com/t/how-many-pounds-of-pressure-does-it-take-to-break-the-average-human-bone/360914/22 "2006-06-19T07:54:30Z")

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You’re not being whooshed. I’m just that thick.

I’m not “getting” the difference between pressure and force. Prehaps if you could express the answer using esamples in clear visual terms so I can “see” it? I’m a fairly visual learner.

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**Author:** ![easy\_e](https://avatars.discourse-cdn.com/v4/letter/e/eb8c5e/32.png) [@easy\_e](https://boards.straightdope.com/u/easy_e)\
**Post date:** [June 19, 2006, 1:27pm UTC](https://boards.straightdope.com/t/how-many-pounds-of-pressure-does-it-take-to-break-the-average-human-bone/360914/23 "2006-06-19T13:27:57Z")

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Just think of it as how its expressed. PSI stands for pounds per square inch. Pressure is defined as force (in this case, pounds) per unit area (inches). Now, you could take that kN figure, convert it to pounds-force, and then calculate what the psi would be if you were applying it with different surface areas. 20 kN will behave a lot differently if you’re applying it with something like a manhole cover (I know it’s odd–it was the first large object that came to mind) than something like a pencil. In the first case, the psi would be lower because you’re applying it with something big. You may not even damage any tissue significantly, other than some bruises. With the pencil, as you can imagine, it would poke right through the skin.

Does that help?

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**Author:** ![Dr\_Paprika](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dr_paprika/32/3042_2.png) [@Dr\_Paprika](https://boards.straightdope.com/u/Dr_Paprika)\
**Post date:** [June 21, 2006, 4:04am UTC](https://boards.straightdope.com/t/how-many-pounds-of-pressure-does-it-take-to-break-the-average-human-bone/360914/24 "2006-06-21T04:04:23Z")

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As mentioned, pressure is force over area. You could shove someone with the same arm force, using your hand (bigger area) or your finger (smaller area). The pressure using your finger would be bigger.

When you talk about an impact force, it is often assumed you are applying it over a small point. Obviously this is an simplified view.

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