Mortgage Calculator
Estimate your monthly mortgage payment including principal, interest, property taxes, insurance, and PMI. Compare different loan scenarios to find the right home financing strategy.
How Mortgage Payments Are Calculated
Understanding the math behind your monthly payment helps you make informed home buying decisions.
A mortgage payment consists of four main components, often referred to as PITI: principal, interest, taxes, and insurance. The principal and interest portion is determined by an amortization formula that ensures equal monthly payments over the life of the loan, while the proportion of each payment going toward principal versus interest shifts over time.
M = P [ r(1+r)n ] / [ (1+r)n - 1 ]
M = monthly payment, P = loan principal, r = monthly interest rate, n = total number of payments
In the early years of a mortgage, the majority of each payment goes toward interest rather than reducing the principal balance. For example, on a $320,000 loan at 6.5% interest, the first monthly payment of $2,023 allocates approximately $1,733 to interest and only $290 to principal. This ratio gradually reverses over the loan term through a process called amortization.
Beyond the base payment, homeowners must also budget for property taxes (typically 1-2% of home value annually), homeowners insurance, and potentially private mortgage insurance if the down payment is less than 20%. These additional costs can add several hundred dollars per month to the total housing expense, which is why lenders evaluate your ability to afford the full PITI payment, not just the principal and interest.
Fixed vs. Adjustable Rate Mortgages
A fixed-rate mortgage locks in the same interest rate for the entire loan term. This provides payment stability and predictability, making it easier to budget long-term. Fixed-rate loans are the most popular choice among homebuyers, particularly during periods of relatively low interest rates when locking in a favorable rate provides lasting value.
An adjustable-rate mortgage (ARM) starts with a lower introductory rate that adjusts periodically after an initial fixed period. A 5/1 ARM, for example, offers a fixed rate for five years before adjusting annually based on a market index. ARMs may make sense for buyers who plan to sell or refinance before the adjustment period begins, but they carry the risk of significantly higher payments if rates increase. The initial savings compared to a fixed-rate loan can be appealing, but borrowers should carefully consider whether they can afford the maximum possible adjusted payment before choosing this option.
How Down Payment Affects Your Mortgage
The size of your down payment directly influences your loan amount, monthly payment, interest costs, and whether you must pay private mortgage insurance. A larger down payment reduces the amount you borrow and can secure a better interest rate, while a smaller down payment preserves cash but increases long-term costs.
Down Payment Comparison on a $400,000 Home
| Down Payment | Loan Amount | Monthly P&I | Monthly PMI | Total Interest (30yr) |
|---|---|---|---|---|
| 5% ($20,000) | $380,000 | $2,402 | ~$158 | ~$484,800 |
| 10% ($40,000) | $360,000 | $2,276 | ~$150 | ~$459,200 |
| 20% ($80,000) | $320,000 | $2,023 | $0 | ~$408,300 |
Estimates based on a 6.5% fixed rate, 30-year term. PMI estimated at 0.5% of loan amount per year.
Putting down 20% instead of 5% on a $400,000 home saves approximately $76,500 in total interest and eliminates the requirement for PMI. However, this requires an additional $60,000 upfront. The right down payment amount depends on your savings, local housing market conditions, and how much liquidity you want to maintain after closing.
When to Consider Refinancing
Refinancing replaces your existing mortgage with a new loan, typically to secure a lower interest rate, shorten the loan term, or switch from an adjustable to a fixed rate. A common guideline is to consider refinancing when you can reduce your interest rate by at least 0.5 to 1 percentage point, although the exact threshold depends on closing costs and how long you plan to remain in the home.
To evaluate whether refinancing makes sense, calculate the break-even point by dividing total closing costs by the monthly savings. If closing costs are $6,000 and the new loan saves $200 per month, you would break even in 30 months. Refinancing is generally worthwhile only if you plan to stay in the home well past the break-even point. Keep in mind that refinancing into a new 30-year term resets the amortization schedule, meaning you may pay more total interest even with a lower rate if you extend the payoff timeline. A shorter-term refinance, such as moving from a 30-year to a 15-year loan, can save substantial interest over the life of the mortgage.
Frequently Asked Questions
Private mortgage insurance (PMI) is required by lenders when your down payment is less than 20% of the home price. It protects the lender in case of default. PMI typically costs between 0.3% and 1.5% of the original loan amount per year. You can avoid PMI by making a 20% or larger down payment. If you already have PMI, you can request its removal once your loan balance reaches 80% of the original home value, or it will automatically terminate at 78%.
A 15-year mortgage has higher monthly payments but saves a significant amount of interest over the life of the loan and typically comes with a lower interest rate. A 30-year mortgage offers lower monthly payments and more cash flow flexibility but costs more in total interest. Choose a 15-year term if you can comfortably afford the higher payments without straining your budget. A 30-year term may be better if you need lower payments or want to allocate extra cash toward other financial goals like retirement investing.
A widely used guideline is that your total monthly housing costs (including principal, interest, taxes, and insurance) should not exceed 28% of your gross monthly income. Your total debt payments, including the mortgage plus other debts like car loans and student loans, should generally stay below 36% of gross income. Lenders may approve higher ratios, but staying within these limits helps ensure your mortgage remains comfortably affordable alongside your other financial obligations.
Closing costs typically range from 2% to 5% of the loan amount and include fees for the appraisal, title search, title insurance, attorney fees, origination fees, and prepaid items such as property taxes and homeowners insurance. On a $320,000 loan, expect to pay between $6,400 and $16,000 in closing costs. Some of these fees are negotiable, and you may be able to ask the seller to contribute toward closing costs as part of the purchase agreement.
This depends on your mortgage interest rate compared to expected investment returns. If your mortgage rate is low (for example, under 5%), investing extra money in a diversified portfolio that has historically averaged higher returns may build more wealth over time. If your mortgage rate is higher, paying it down provides a guaranteed return equal to the interest rate you save. Many financial planners recommend a balanced approach: make regular mortgage payments while also contributing to retirement accounts and maintaining an emergency fund. The psychological benefit of being debt-free is also a valid factor in this decision.
