The home affordability calculator from realtor.com® helps you estimate how much house you can afford. Quickly find the maximum home price within your price range., This home price might be difficult to afford. A DTI ratio above 43% can signal to lenders that you may find it challenging to pay debt., To calculate how much house you can afford, use the 25% guideline we talked about earlier: Never spend more than 25% of your monthly take-home pay (after tax) on monthly mortgage payments. That includes your mortgage principal, interest, property taxes, home insurance, private mortgage insurance (PMI) and homeowners association (HOA) fees., , , .