What Makes Up a Mortgage Payment? (PITI)
When lenders quote a monthly mortgage payment, they usually mean PITI — the four components that make up your total housing cost each month:
- Principal — the portion of your payment that pays down the loan balance itself.
- Interest — the cost of borrowing, calculated on your remaining balance each month.
- Taxes — property taxes, collected monthly into an escrow account and paid to your local tax authority.
- Insurance — homeowner’s insurance, plus private mortgage insurance (PMI) if your down payment is below 20%.
Principal and interest are fixed on a fixed-rate loan. Taxes and insurance can change year to year, so your total payment can drift even on a “fixed” mortgage.
The Mortgage Payment Formula
The principal-and-interest portion of your payment is calculated with the standard amortization formula:
M = P × r(1+r)n ÷ ((1+r)n − 1)
Where P is the loan amount, r is the monthly interest rate (annual rate ÷ 12), and n is the number of monthly payments. For example, a $320,000 loan at 6.5% for 30 years has a monthly rate of 0.005417 and 360 payments — plugging those in gives a principal-and-interest payment of about $2,022 per month.
Rather than doing that math by hand, use a mortgage payment calculator to get the number instantly and adjust the inputs to see how each factor changes your payment.
How Rate, Term, and Down Payment Affect Your Payment
Interest rate
Rate is the biggest lever. On a $320,000 loan at 6.5% for 30 years, you pay about $2,022/month in principal and interest. At 7.5%, that jumps to roughly $2,237 — an extra $215 every month, or nearly $77,000 over the life of the loan. Even a quarter-point difference matters when the balance is large.
Loan term
A 15-year term roughly doubles your monthly payment but cuts total interest dramatically. That same $320,000 at 6.5% for 15 years costs about $2,788/month — $766 more per month — but total interest drops from around $408,000 to about $182,000. Run both scenarios in a mortgage payment calculator before deciding which term fits your budget.
Down payment
A bigger down payment shrinks the loan amount (P in the formula) directly, lowering every payment. It also has a second effect: put down 20% or more and you avoid PMI entirely. Put down less and you add a monthly PMI premium — often $50 to $200+ per month — on top of the payment until you reach 20% equity.
Understanding PMI
Private mortgage insurance protects the lender, not you, and you pay for it when your down payment is below 20% on a conventional loan. PMI typically costs 0.5% to 1.5% of the loan amount per year, divided into monthly payments. On a $320,000 loan, that’s roughly $133 to $400 per month added to your payment.
The good news: PMI isn’t permanent. By law, it must be removed once your balance reaches 78% of the home’s original value through normal payments. You can request removal at 80% loan-to-value, and rising home values can get you there faster — a refinance to drop PMI is one of the most common reasons homeowners refinance, which you can evaluate with a refinance calculator.
Worked Example: $400,000 Home in 2026
Let’s walk through a realistic 2026 purchase. You’re buying a $400,000 home with 10% down at 6.5% on a 30-year fixed loan:
- Down payment: $40,000
- Loan amount: $360,000
- Principal & interest: about $2,275/month
- Property tax (1.1% of home value): about $367/month
- Homeowner’s insurance: about $150/month
- PMI (0.7% of loan): about $210/month
- Total monthly payment: about $3,002/month
Now see what changes if you put 20% down instead ($80,000): the loan drops to $320,000, P&I falls to about $2,022, and PMI disappears completely — the total drops to roughly $2,539/month. That’s a savings of over $460 every month.
Before locking in a purchase price, it’s worth checking whether the home fits your income in the first place. A mortgage affordability calculator uses the 28/36 rule to estimate how much house you can actually afford, and then a mortgage payment calculator turns that price into the exact monthly number you’ll pay.
Fixed vs. Adjustable Rates: How They Change the Math
Everything above assumes a fixed-rate mortgage, where principal and interest never change. With an adjustable-rate mortgage (ARM), your rate — and therefore your payment — resets after an initial fixed period, often 5, 7, or 10 years. A 5/1 ARM might start a full point below a 30-year fixed, saving you hundreds per month in the early years.
The trade-off is uncertainty. If rates rise, your payment can jump at each reset, sometimes dramatically. ARMs make sense if you’ll sell or refinance before the first adjustment, but for a long-term home, the stability of a fixed rate is usually worth the premium. Either way, a mortgage payment calculator lets you compare the initial ARM payment against the fixed-rate alternative side by side.
Escrow Accounts: Why Your Payment Includes More Than the Loan
Most lenders require an escrow account when your down payment is under 20%, and many borrowers keep one voluntarily. Each month, the lender collects one-twelfth of your annual property tax and homeowner’s insurance bills on top of your principal and interest, holds the money, and pays the bills when they’re due.
Escrow protects both sides — the lender knows taxes and insurance won’t lapse — but it means your total payment can rise even with a fixed loan if property taxes or insurance premiums increase. When that happens, the lender performs an annual escrow analysis and adjusts your monthly collection. It’s not the lender pocketing extra money; it’s the real cost of taxes and insurance going up.
Tips to Lower Your Mortgage Payment
- Increase your down payment to borrow less and eliminate PMI.
- Improve your credit score before applying — a higher score unlocks lower rates.
- Compare at least 3 lenders; rate offers can differ by a quarter point or more.
- Consider buying points — paying an upfront fee to lower the rate can pay off if you stay long enough.
- Choose a longer term if cash flow is tight, then make extra principal payments when you can.
Your mortgage payment is the single largest line item in most household budgets. Understanding the formula, testing scenarios, and comparing offers puts you in control — run the numbers on a mortgage payment calculator before you make an offer, and revisit them every year to see if a refinance could lower what you pay.