I need to calculate my w4 since I am starting a new job and have a new salary. I also will be contributing to a 403b plan at the max amount and so will my spouce

I need to calculate my w4 since I am starting a new job and have a new salary. I also will be contributing to a 403b plan at the max amount and so will my spouce.  


Turbo tax advice was to go to the IRS website.  This is not helpful.  Why am I paying to use TurboTax when their answer is go to the irs website?