Do you know the planner in the opposite direction? A first step for us before planning a trip.
Of course, you must already know your itinerary. This site has helped us a lot to get an idea of the daily cost per country.
In total on all our itinerary he calculated us an average daily budget of 27€ per person. In order to make a small margin we rounded it up to 30€.
This amount includes accommodation, food and transportation. It is an average so we are well aware that we will be well below in Asia, which will allow us to compensate in New Zealand and South America.
Another source of information for the daily budget: bloggers’ travel websites again and again. Some of them make very complete country-by-country assessments with details of their budget spent on the spot.