Your monthly payment depends on three things: the interest rate, the loan term, and whether you have an escrow account
On a $120,000 mortgage, your monthly payment (principal and interest only) typically ranges from $570 to $1,100, depending on the interest rate and how many years you have to repay. A 30-year loan at 7% interest costs about $798 per month. The same loan at 5% costs about $644 per month. At 6%, you pay roughly $719 per month.
These numbers assume you are paying only the loan itself—not property taxes, homeowners insurance, or mortgage insurance, which most lenders require you to pay alongside your mortgage payment. Your actual monthly bill will be higher once those are added in. The total is often called your PITI payment: principal, interest, taxes, and insurance.
The interest rate you receive depends on your credit score, the size of your down payment, current market rates, and the lender you choose. Rates change daily. A difference of even 0.5% in your interest rate changes your monthly payment by roughly $30 to $40 on a $120,000 loan.
Key Takeaways
- A $120,000 mortgage at 6% interest over 30 years costs about $719 per month in principal and interest alone.
- Your actual monthly payment will be higher because it includes property taxes, homeowners insurance, and possibly mortgage insurance.
- A 15-year loan costs more per month but you pay far less interest overall—roughly $50 to $100 more monthly than a 30-year loan on the same amount.
- Your interest rate is set by your lender based on your credit score, down payment size, and current market conditions, and it has the single largest effect on your monthly cost.
How interest rate changes affect your payment
The interest rate is the percentage of the loan amount you pay to the lender each year. On a $120,000 loan, even a small change in rate shifts your monthly payment noticeably. Here is how the numbers move across common rates on a 30-year loan:
| Interest Rate | Monthly Payment (Principal & Interest) | Total Interest Paid Over 30 Years |
|---|---|---|
| 4% | $573 | $86,300 |
| 5% | $644 | $111,700 |
| 6% | $719 | $138,800 |
| 7% | $798 | $167,500 |
| 8% | $880 | $196,800 |
The difference between a 5% rate and a 7% rate is $154 per month—nearly $1,850 per year. Over the life of the loan, you pay an extra $55,800 in interest. This is why your credit score and down payment size matter so much: they directly determine which interest rate you receive.
Loan term: 15 years versus 30 years
A 15-year mortgage has a higher monthly payment but you pay the loan off faster and pay far less interest overall. On a $120,000 loan at 6% interest, a 15-year term costs about $889 per month—roughly $170 more than a 30-year loan. But you pay only $40,000 in total interest instead of $138,800.
A 30-year mortgage has a lower monthly payment, which makes it easier to fit into your budget each month. You pay more interest over time, but you have more flexibility if your income changes or you face an unexpected expense. Most borrowers choose 30-year loans because the monthly cost is lower.
Some lenders offer 20-year or 25-year terms as well. The longer the term, the lower your monthly payment but the more interest you pay. The shorter the term, the higher your monthly payment but the less interest you pay overall.
What gets added to your principal and interest payment
Your lender will require you to pay more than just principal and interest each month. Most lenders use an escrow account, which means they collect money from you monthly for property taxes and homeowners insurance, then pay those bills on your behalf when they are due.
If you put down less than 20% of the home's purchase price, your lender will also require private mortgage insurance (PMI). This protects the lender if you stop paying. PMI typically costs 0.5% to 1% of your loan amount per year, added to your monthly payment. On a $120,000 loan, that is roughly $50 to $100 per month.
Property taxes vary by location and are assessed by your county or municipality. Homeowners insurance also varies by location, home age, and coverage level. On a $120,000 home in a moderate-cost area, combined taxes and insurance might add $200 to $400 per month to your payment. In high-cost areas, they can add $500 or more.
How to estimate your total monthly payment
Start with your principal and interest amount from the table above, based on your interest rate and loan term. Then add an estimate for taxes and insurance. If you do not know your local property tax rate, contact your county assessor's office or ask a local real estate agent. For insurance, get quotes from at least two insurers.
If your down payment is less than 20%, add PMI. Divide your loan amount by 100, then multiply by 0.75 (a middle estimate for PMI cost). On a $120,000 loan, that is roughly $900 per year, or $75 per month. Your lender will give you an exact PMI quote when you apply.
Example: A $120,000 mortgage at 6% over 30 years, with $300 per month in taxes and insurance, and $75 per month in PMI, totals roughly $1,094 per month. This is the amount you will actually pay to your lender each month.
How your credit score affects the rate you receive
Lenders use your credit score to decide what interest rate to offer. A higher score means lower risk to the lender, so you get a lower rate. A lower score means higher risk, so you pay a higher rate. The difference between a score of 620 and a score of 760 can be 1% to 2% in interest rate—which translates to $120 to $240 per month on a $120,000 loan.
If your credit score is below 620, many conventional lenders will not work with you. You may need to look at FHA loans, which allow scores as low as 500 but require mortgage insurance regardless of your down payment size. If your score is between 620 and 680, you will pay a higher rate than someone with a score above 740.
Before you apply for a mortgage, check your credit report for errors and dispute any you find. Paying down existing debt and making all payments on time for several months can raise your score and lower the rate you receive.
Down payment size and its effect on your payment
The larger your down payment, the smaller your loan amount and the lower your monthly payment. A 20% down payment on a $120,000 home is $24,000, leaving a $96,000 loan. A 10% down payment is $12,000, leaving a $108,000 loan. A 3% down payment is $3,600, leaving a $116,400 loan.
Down payment size also affects your interest rate. Lenders offer better rates to borrowers who put down 20% or more because they have more skin in the game. If you put down less than 20%, you will pay PMI and may receive a slightly higher interest rate as well.
If you cannot save 20% before buying, putting down as much as you can afford still helps. Even a 5% or 10% down payment lowers your loan amount and your monthly cost. Some first-time buyer programs allow down payments as low as 3%.
Frequently Asked Questions
What is the difference between a fixed-rate and adjustable-rate mortgage?
A fixed-rate mortgage keeps the same interest rate for the entire loan term—30 years, 15 years, or whatever you choose. An adjustable-rate mortgage (ARM) starts with a lower rate for a set period (often 3 to 7 years), then adjusts up or down based on market conditions. Fixed-rate mortgages are more predictable; ARMs can save money upfront but carry the risk of higher payments later.
Can I pay extra toward principal each month?
Yes. Most lenders allow you to pay extra toward principal without penalty. Paying an extra $100 or $200 per month shortens your loan term and saves you thousands in interest. Check your loan documents or ask your lender whether there are any prepayment penalties—most mortgages do not have them, but some do.
What happens if interest rates drop after I lock in my rate?
You can refinance your mortgage, which means taking out a new loan to pay off the old one. Refinancing has closing costs (typically 2% to 5% of the loan amount), so it only makes sense if rates drop enough to offset those costs. A drop of 0.5% to 1% usually justifies refinancing; a drop of 0.25% usually does not.
How do I know if I can afford a $120,000 mortgage?
Most lenders use a debt-to-income ratio: your total monthly debt payments (including the new mortgage) should not exceed 43% of your gross monthly income. On a $120,000 loan with a $1,100 monthly payment, you need a gross monthly income of roughly $2,560 to meet this threshold. Your lender will verify your income and run this calculation before approving you.
What if my interest rate is locked but rates drop before closing?
Once you lock in a rate, it is fixed until your closing date—usually 30 to 45 days later. If rates drop, you cannot change your rate unless you pay a fee to unlock and re-lock at the new rate. Some lenders offer a free rate-drop option, but it costs more upfront. Ask your lender what options are available when you lock your rate.