To get the most useful estimate, have your target home price, estimated down payment, preferred loan term, and an approximate interest rate ready. If you already know the property tax rate or HOA fee, include those as well.
Buyers who are still early in the process can still use the page by testing a few plausible scenarios. That is often enough to tell whether a home fits your budget before you tour properties or submit an offer.
The calculator is also helpful if you want to compare a conservative budget with a stretch budget and see which option leaves more room for savings, maintenance, and other monthly bills.