How much Crit Chance does a power charge grant?

and by that I mean how much does it actually translate to? cause an item will say 30% crit chance but in reality its just 1% crit chance on main hand.

depends on your weapons or spells base crit chance
your item will give you 30%

this weapon has 5% chance to crit. so your items extra 30% would give around 1.5% bonus crit chance

A power charge gives 40% increased crit chance. The actual +crit chance that gives you is just 40% of whatever your base crit chance is. For example, if you're using a spell or weapon with 5% base crit (and have no other sources of base crit) then it would be 2% extra crit chance.

Thanks