I've made an Onigiri Damage Calculator which isn't so useful for most people (but I'll put it here anyway). It's not exact but it does get close.
Damage And Stat Calculator v2.1.
I wrote it in C so it might say something like "unknown publisher" but the source code is also there if you want to compile it yourself for whatever reason.
Nothing much else to say here since there are instructions included. I think I've covered most things there but feel free to let me know if I've missed something or if you have any questions.
Enjoy.
Edit: I should probably mention that some skill multihit cut values on the wiki are incorrect since there should be a default value of 50 when it's not included.