That is a odd question that I don't know how to answer.
Likely the output current is 1/4 the input current.
Are you running 50/60hz AC into the quadrupler and then getting DC voltage out? The output current is a function of the current the transformer is rated for.
Presumably this is in relation to your other thread?, you don't have any power to quadruple, and the resultant current (if it works at all) would be less than 1/4 of the input current.
The other thread is about flexing two piezos to make harvested energy. But the current is extremely small from the piezos then the current of this voltage multiplier will be less than one-quarter of the original extremely small current which results in A WASTE OF TIME.
It might take many years for flexing the piezos to charge his little 9V battery.