Mortgage Calculator

Your monthly P&I uses M = P × [r(1+r)^n] / [(1+r)^n − 1], where P = loan amount, r = monthly rate (annual ÷ 12), n = total payments. A $400,000 loan at 6.8% for 30 years = ~$2,610/month P&I. Add property tax, home insurance, PMI, and HOA to get your full PITI payment.

Private Mortgage Insurance is required on conventional loans when your down payment is less than 20%. PMI typically costs 0.5–1.5% of the loan per year. Once your balance reaches 80% LTV you can request cancellation under the Homeowners Protection Act. FHA loans use MIP instead, which works differently (often stays for the life of the loan).

30-year has lower monthly payments but 2–3× more total interest. 15-year has ~40–50% higher payments but ~55% less interest and builds equity faster. 15-year rates are also typically 0.5–0.75% lower. Choose 30-year for cash flow flexibility; choose 15-year if you want to minimize total interest cost and can handle the higher payment.

The 28/36 rule: housing payment (PITI) ≤ 28% of gross monthly income, total debt ≤ 36%. Lenders typically allow DTI up to 43–45%. On $80k/year ($6,667/month gross), the 28% rule gives a max housing payment of ~$1,867/month. Factor in property taxes and insurance — they can add $500–$1,000+/month on a $400k home.

Amortization shows how each payment splits between principal and interest over time. Early payments are mostly interest — on a 30-year mortgage you won't cross the 50% paydown point until roughly year 18–19. Extra principal payments early have an outsized impact because they reduce the balance on which future interest accrues.