Is there a way to objectively measure

pain? Like, if you hit your finger with a hammer you suffer 5.7 units of pain?

>>40
what do you mean by pun? Serious subject is serious. :|

There Is A Simple Scale For Measuring Pain.
relevant paper:
A simple pain scale for field comparison of Hymenopteran stingsckstarr.net [PDF]
CK Starr - Journal of Entomological Science, 1985 - ckstarr.net

but there is also the Schmidt Sting Pain Index - look it up on wikipedia.
the pain of giving birth is considered the most painful pain, iirc?

While it is difficult to measure pain directly, you can always approximate it indirectly since it has a strong correlation with gain.