Polls are medians of surveys in the last 1-3 weeks. as tracked at HuffPollster. Boundary county and Google Correlate-based estimates are done using the method described here and further explained here.
The delegate estimate in the banner of this website is calculated using delegate rules as documented at The Green Papers and implemented using a custom MATLAB script. Its inputs are state polls where available. Where no polls are available, boundary-county-based estimates are used (at some point this may switch to Google Correlate-based estimates).