True Cost of Ownership Calculator Explained (2026)

Quick answer: Your true monthly cost of homeownership is roughly 1.35–1.60× your mortgage principal & interest payment once property taxes, homeowners insurance, PMI, HOA, utilities, and a maintenance reserve are added. On a $400,000 home with 10% down at a 6.75% mortgage rate, the P&I is $2,335/month — but the true monthly cost is $3,850–$4,200/month before you spend a dollar on furniture.

Standard mortgage calculators (Bankrate, Zillow, NerdWallet) return one number: principal and interest. That number is useful for qualifying, not for living. This guide walks through the eight components of a real True Cost of Ownership figure, shows the formula, and lets you sanity-check any calculator's output. Pair it with our full PITI+PMI calculator to see all eight numbers side-by-side.

The HomeScore True Cost of Ownership formula is: