The basic formula: principal, interest, taxes, and insurance

Your monthly mortgage payment has four parts, often called PITI. The lender calculates principal and interest based on your loan amount, interest rate, and loan term. Then your servicer adds property taxes and homeowners insurance, which vary by location and your home's value. The total is what you send in each month.

The principal and interest portion stays the same for the life of a fixed-rate loan — that math is locked in at closing. Taxes and insurance can change year to year, so your payment may shift even though your loan terms do not. If you put down less than 20 percent, mortgage insurance (PMI) gets added too, and that also changes the monthly total.

Key Takeaways

  • Principal and interest are calculated using your loan amount, interest rate, and loan term — a 30-year loan at 6.5 percent on $300,000 produces a different payment than a 15-year loan at the same rate.
  • Property taxes and homeowners insurance are added to principal and interest, and both can increase over time, raising your payment even if your loan balance does not.
  • If your down payment was less than 20 percent, mortgage insurance (PMI) is included in your payment and can be removed once you reach 20 percent equity.
  • The amortization schedule determines how much of each early payment goes to interest versus principal — early payments are mostly interest, later ones mostly principal.

How principal and interest are split across your payment

In the first months of your loan, most of your payment goes toward interest, not principal. This surprises many homeowners. On a $300,000 loan at 6.5 percent over 30 years, your first payment might be roughly $1,896 per month (principal and interest only), but only about $400 of that reduces what you owe — the rest pays the lender's interest.

This split is determined by an amortization schedule, which the lender provides at closing. As you pay down the balance, the interest portion shrinks and the principal portion grows. By year 20 of a 30-year loan, you might be paying $800 toward principal and $600 toward interest in the same $1,400 payment. This is why paying extra toward principal early in the loan saves significant interest over time.

Where property taxes fit into your payment

Most homeowners do not pay property taxes directly to the county. Instead, the lender collects one-twelfth of your annual property tax bill each month and holds it in an escrow account. When taxes are due, the lender pays the county from that account on your behalf. This protects the lender — unpaid property taxes can become a lien on the home.

Property tax rates vary widely by county and state. A $400,000 home in one county might carry $4,000 in annual taxes, while the same home elsewhere costs $8,000 or more. When your county reassesses your home's value (often every few years), your property tax bill changes, and so does your monthly payment. The lender adjusts your escrow payment to match.

How homeowners insurance is bundled into your payment

Like property taxes, homeowners insurance is usually collected monthly by your lender and held in escrow. You do not pay the insurance company directly; the lender pays them when the annual premium is due. This ensures the home stays insured — an uninsured home is a lender's nightmare.

Insurance premiums depend on the home's replacement cost, your location (flood zone, crime rate, distance to fire station), the age of the roof and foundation, and your claims history. A new home in a low-risk area might cost $1,200 per year to insure; an older home in a high-risk zone could be $3,000 or more. When you renew your policy each year, the premium may increase, and your lender adjusts your monthly payment accordingly.

Mortgage insurance (PMI) and when it disappears

If you put down less than 20 percent, the lender requires private mortgage insurance (PMI). This protects the lender if you default — it is not insurance for you. PMI typically costs 0.5 to 1.5 percent of your loan amount per year, added to your monthly payment.

PMI can be removed once you reach 20 percent equity in the home. This happens through a combination of paying down the principal and the home appreciating in value. On a $300,000 home with a $60,000 down payment (20 percent), you start with 20 percent equity and never pay PMI. On the same home with a $30,000 down payment (10 percent), you need the home to be worth $375,000 or your loan balance to drop to $300,000 — whichever comes first — before PMI can be removed. You can request removal once you hit that threshold; the lender may require an appraisal to confirm.

How interest rates change your monthly payment

A higher interest rate raises your monthly payment significantly, even on the same loan amount and term. A $300,000 loan at 5 percent over 30 years costs roughly $1,610 per month (principal and interest). The same loan at 7 percent costs roughly $1,996 per month — nearly $400 more, every month, for 30 years. That is $144,000 in extra payments over the life of the loan.

Interest rates are set by the market and your lender's assessment of risk. Your credit score, down payment size, loan-to-value ratio, and the type of property all affect the rate you are offered. A 0.5 percent difference in rate can mean tens of thousands of dollars over the loan term, which is why shopping multiple lenders before locking in a rate matters.

Loan term and how it affects what you pay monthly

A shorter loan term means a higher monthly payment but far less interest paid overall. A $300,000 loan at 6.5 percent costs roughly $1,896 per month over 30 years, totaling about $682,000 in payments. The same loan over 15 years costs roughly $2,596 per month, totaling about $467,000 — you pay $215,000 less in interest, but your monthly payment is $700 higher.

The choice between a 30-year and 15-year mortgage (or other terms like 20-year) depends on your cash flow and goals. A 30-year loan is easier on monthly budget but costs more over time. A 15-year loan builds equity faster and costs less total, but requires a larger monthly payment. Some homeowners refinance from 30 to 15 years partway through, once their income has grown or they have paid down the balance.

What happens when taxes or insurance increase

Your property tax bill or insurance premium can rise without your loan terms changing at all. When this happens, your lender recalculates your escrow payment and adjusts your monthly bill upward. You will see this reflected in a new payment coupon or statement from your servicer.

Some lenders build a small cushion into your escrow account to absorb small increases. If the cushion is not enough, you may owe a lump sum at the end of the year, or the lender may spread the shortage across the next 12 months. Conversely, if taxes or insurance drop, you may receive a refund or a credit toward future payments. Always review your escrow statement each year — errors happen, and you have the right to dispute them.

Frequently Asked Questions

Why does my payment go up if my loan balance is going down?

Your principal and interest payment stays the same on a fixed-rate loan, but property taxes or insurance can increase independently. When the county reassesses your home's value or your insurance company raises rates, the lender adjusts your escrow payment upward. This is normal and separate from paying down your loan.

Can I pay extra toward principal without refinancing?

Yes. Most lenders allow you to send extra money with your payment and specify that it goes toward principal. This reduces your loan balance faster, cuts the total interest you pay, and can shorten your loan term. Check your loan documents or call your servicer to confirm they accept extra principal payments without penalty.

What is the difference between a fixed-rate and adjustable-rate mortgage payment?

A fixed-rate mortgage has the same principal and interest payment for the entire loan term. An adjustable-rate mortgage (ARM) has a lower rate for an initial period (often 3, 5, 7, or 10 years), then adjusts annually based on market conditions. After the fixed period ends, your payment can increase significantly, sometimes by hundreds of dollars per month.

How do I know how much of my payment goes to principal versus interest?

Your lender provides an amortization schedule at closing that shows the breakdown for each payment. You can also request one from your servicer at any time, or calculate it using online amortization calculators. Early in the loan, most goes to interest; later, most goes to principal.

What happens if I miss a payment?

Missing a payment triggers late fees and can damage your credit score. After 30 days, the lender reports it to credit bureaus. After 120 days, foreclosure proceedings may begin. Contact your servicer immediately if you cannot pay — many offer forbearance or loan modification options that can prevent foreclosure.