Self employed

The reason I came up with the extra $200 in withholding from my regular job was: 

15% of $25k in freelance = $3750 in probable taxes 

$3750 divided by 26 paychecks = $145 approximately 

(I set it to $200 just to be extra careful!)

 

So I figured after the extra withdrawals I set up at the end of the year there shouldn't be any more owed - and maybe even still a little return back. 

 

Does that make sense? That means I shouldn't have to pay a quarterly amount if I do this, right? 

 

Thanks for the help!