Mortgage Calculator with Extra Payments & Amortization Schedule

A standard fixed-rate mortgage payment is computed using the amortization equation M = P × [r(1+r)^n] / [(1+r)^n - 1], where P is principal loan balance, r is the monthly interest rate (annual APR / 12), and n is total monthly payments (years × 12). Total monthly payment also includes escrow reserves for property taxes, homeowners insurance, and private mortgage insurance (PMI) if down payment is below 20%.

Because mortgage amortization is heavily front-loaded with bank interest in the initial 10 to 15 years, paying just an additional $100 to $200 per month directly toward the principal balance can shave 4 to 7 years off a 30-year loan and save $30,000 to $65,000 in total interest charges.

PMI is required by conventional mortgage lenders when the down payment is less than 20% of the purchase price. Under the federal Homeowners Protection Act, lenders must automatically cancel PMI once your principal balance drops to 78% of the original purchase value, or you can request cancellation once you reach 80% equity.

A 15-year fixed mortgage has higher monthly payments (typically 35% to 45% higher) because the principal is repaid twice as fast, but carries a lower interest rate (usually 0.5% to 0.75% lower) and reduces total lifetime interest paid by more than 60% compared to a 30-year loan.

Escrow accounts hold funds collected monthly by your lender to pay annual municipal property taxes and homeowners insurance premiums on your behalf. Even on a fixed-rate mortgage, your total monthly outlay changes annually if local property assessments or insurance premiums increase.