Calculation of Critical Hit. PLEASE HELP.

Suntzu1414

Thank you for taking time to read my post.

I'm trying to understand the difference in damage (using bow) between:

1. light attack
2. heavy attack
3. critical attack

I seen a lot of posting on this topic.
But, none that break out the mech and damage done by crit (vs light vs heavy).

I know it will matter on the equipment and stamina you have.
BUT, is there a RULE of THUMB...regarding crit damage??

thank you in advance.
st

PS Sorry in advance if this has already been posted. I just couldn't find it.