How mortgage payments work

A monthly mortgage payment is really several bills folded into one. The part that repays the loan, called principal and interest (P&I), is fixed for the life of a fixed-rate mortgage, while property taxes, homeowner's insurance, private mortgage insurance (PMI) and any homeowners association (HOA) dues are added on top and can change from year to year. Knowing which part is which makes it much easier to read a loan estimate, a monthly statement or a calculator result.

The parts of a housing payment

Lenders often use the shorthand PITI: principal, interest, taxes and insurance. Two more items apply to many borrowers.

• Principal is the part of each payment that reduces the amount you borrowed.
• Interest is the lender's charge for the money still outstanding. On a standard fixed-rate loan it is calculated each month as the current balance multiplied by the annual rate, divided by 12.
• Property taxes are set by your local government and usually collected by the lender in monthly installments through an escrow account, then paid on your behalf when the tax bill is due.
• Homeowner's insurance protects the property and is typically collected the same way, one-twelfth of the annual premium each month.
• Private mortgage insurance (PMI) is generally required on a conventional loan when the down payment is below 20 percent of the price, meaning the loan-to-value (LTV) ratio is above 80 percent. It protects the lender, not you, and it is usually removed once the balance falls far enough.
• HOA dues apply to condos and many planned communities. They are paid to the association rather than the lender, but they are still part of what the home costs each month.

Principal and interest are the "loan" part of the payment; everything else is a cost of owning the home collected at the same time.

How the fixed P&I payment is set

A fully amortizing fixed-rate mortgage is designed so that one constant monthly payment, made every month for the whole term, pays all of the interest and brings the balance to exactly zero with the last payment. Three inputs determine that payment: the loan amount, the annual interest rate and the number of monthly payments.

M = P × r × (1 + r)^n ÷ ((1 + r)^n − 1)

The payment depends only on those three numbers. Once the loan closes, the P&I amount on a fixed-rate loan does not move, even though the split between principal and interest inside it changes every month. An adjustable-rate loan is different: its rate, and therefore its payment, can reset after an initial period.

Why early payments are mostly interest

Each month the lender first calculates interest on the balance you still owe. Whatever is left of the fixed payment after covering that interest goes to principal. Because the balance is largest at the beginning, the interest charge is largest at the beginning too, and only a small slice of the payment reduces the loan.

As the balance shrinks, the interest charge shrinks with it, so a larger share of the same payment goes to principal. This gradual shift is called amortization, and you can read more about it in what amortization is and where each payment goes.

A worked example: $300,000 at 6.5% for 30 years

Suppose you borrow $300,000 at a fixed 6.5 percent rate over 30 years (360 payments). Based on those inputs, the estimated P&I payment is about $1,896 per month, and the estimated interest over the full term is approximately $382,600. Put another way, you would repay the $300,000 you borrowed plus roughly $382,600 in interest, for an estimated total of about $682,600 in principal and interest.

In the first month, interest on the full $300,000 balance is $300,000 × 6.5% ÷ 12 = $1,625. That leaves only about $271 of the $1,896 payment to reduce the loan. Thirty years later the final payment is almost all principal: roughly $10 of interest and about $1,891 of principal.

Principal does not overtake interest within a single payment until payment 233, more than 19 years in. After 15 years, about $259,000 has gone to interest and only about $82,300 to principal, leaving an estimated balance near $217,700. These figures are estimates based on the assumptions entered and assume every payment is made on time.

A full housing payment example

Now add the other parts. Imagine a $450,000 home with a 10 percent down payment of $45,000, so the loan amount is $405,000 and the LTV is 90 percent. Keep the same 6.5 percent rate and 30-year term, and assume property taxes of $5,400 per year, homeowner's insurance of $1,800 per year and HOA dues of $100 per month.

Only the $2,560 of P&I is repaying the loan; the other $869 covers taxes, insurance, PMI and dues. Because the down payment is under 20 percent, PMI is included at an assumed 0.5 percent annual rate. Under this schedule the balance would reach 78 percent of the original price after about 109 payments, at which point PMI would typically stop and the estimated payment would drop to about $3,260. Actual PMI depends on your credit profile, loan type and lender; see what PMI is and when it goes away. Taxes and premiums are also reassessed regularly and usually rise, so the escrow portion tends to change even when P&I stays fixed.

What changes the payment

• Interest rate. This has the biggest effect per unit of change. On the $300,000 loan, a rate of 6 percent instead of 6.5 percent would lower the estimated P&I payment to about $1,799 and total interest to roughly $347,500, a saving of approximately $35,000 over the term.
• Loan term. A shorter term means a higher payment but far less interest. The same $300,000 at 6.5 percent over 15 years has an estimated P&I payment of about $2,613, roughly $717 more per month, but total interest of approximately $170,400 instead of $382,600.
• Loan amount and down payment. A larger down payment reduces the loan, which reduces both P&I and interest, and if it brings the LTV to 80 percent or below it can remove PMI entirely. You can explore this in down payments explained.
• Taxes, insurance and HOA dues. These do not affect the loan math, but they can add hundreds of dollars a month and vary widely by location.
• Extra principal. Paying more than the scheduled amount does not change the fixed P&I payment. It reduces the balance faster, so less interest accrues and the loan ends sooner. Adding $250 per month to the $300,000 example would save an estimated $120,300 of interest and shorten the payoff by about 8 years 2 months.

Common mistakes and misconceptions

1. Comparing a P&I quote to a full housing payment. A figure that shows only principal and interest will look far cheaper than one that includes taxes, insurance and PMI.
2. Assuming the payment never changes. On a fixed-rate loan the P&I portion is fixed, but the escrow portion can rise when taxes or premiums increase, and PMI usually drops off part-way through.
3. Expecting half the loan to be paid off at the halfway point. Because early payments are mostly interest, the balance falls slowly at first. In the example above, less than a third of the loan was repaid after 15 of 30 years.
4. Forgetting HOA dues. They are billed separately from the lender's payment, but a budget that leaves them out understates the cost of the home.
5. Treating PMI as permanent. PMI on a conventional loan is designed to end once the balance reaches a set share of the original value, and borrowers can often request cancellation earlier.
6. Reading estimates as quotes. Rates, taxes, insurance and PMI all vary by lender, location and time. Calculator results are estimates based on the assumptions entered, not an offer.

Principal and interest (P&I)

The part of the monthly payment that repays the loan itself: the amount borrowed plus the lender's charge on the outstanding balance.

Escrow account

An account the lender maintains to collect property taxes and insurance premiums in monthly installments and pay the bills when they come due.

Loan-to-value (LTV)

The loan amount divided by the home's price or appraised value, expressed as a percentage. A 10 percent down payment produces a 90 percent LTV.

Amortization

Paying off a loan with fixed payments where the share going to principal grows over time as the interest charge shrinks.

Total monthly housing payment

P&I plus taxes, insurance, PMI and HOA dues: the full amount paid each month for the home.

Try it with your own numbers

Enter a price, down payment, rate and term, then add your local tax and insurance estimates to see how the pieces of an estimated total monthly housing payment fit together and how the split shifts over the years. Try it in the mortgage calculator