Calculate monthly payments and loan amortization
A mortgage is a loan used to purchase real estate, where the property serves as collateral. Monthly payments typically include principal (loan amount), interest, property taxes, and insurance (PITI). Understanding mortgage calculations helps you make informed decisions about home buying and refinancing.
M = P[r(1+r)^n]/[(1+r)^n-1] where P = principal, r = monthly rate, n = number of payments
| Calculation | Expression | Result |
|---|---|---|
| 30-year mortgage | $300,000 at 6.5% | $1,896.20/month |
| 15-year mortgage | $200,000 at 5.5% | $1,634.17/month |
| With 20% down | $400,000 home, 20% down | $320,000 loan |
The payment is calculated using an amortization formula that ensures the loan is fully paid off by the end of the term. It factors in the loan amount, interest rate, and loan term. Most of early payments go toward interest, gradually shifting toward principal over time.
Private Mortgage Insurance (PMI) protects the lender if you default. It's typically required when your down payment is less than 20% of the home's value. PMI usually costs 0.5-1% of the loan annually and can be removed once you reach 20% equity.
A 15-year mortgage has higher monthly payments but lower total interest and a lower rate. A 30-year mortgage has lower payments but higher total cost. For a $300,000 loan at typical rates, a 30-year might pay $150,000+ more in interest over the life of the loan.
Extra payments go directly to principal, reducing interest over the life of the loan. Adding just $100/month to a $300,000, 30-year mortgage at 6% can save over $50,000 in interest and pay off the loan 5 years early.
An escrow account holds funds for property taxes and insurance. Your monthly payment includes a portion that goes into escrow. The lender pays taxes and insurance from this account when due, ensuring these important payments aren't missed.
Consider refinancing when rates drop at least 0.5-1% below your current rate, you plan to stay in the home long enough to recoup closing costs (typically 2-4 years), or you want to change loan terms. Calculate your break-even point by dividing closing costs by monthly savings.