Mortgage calculators are too simple to factor taxes in because it can be drastically different and complicated. For it to be accurate it would have to account for deduction phase outs, AMT rules and many other factors. It’s too complicated to boil down to a simple formula for all people, even though in your case it might be quite simple.
As for figuring it out for your paprticular circumstances. I would definitiely figure out the tax impacts in my analysis of what I could afford. Do not make too many assumptions or use rules of thumb. You wouldn’t make a monthly budget without considering how much you take home versus gross income. Same thing with budgeting for a house.
