How to Calculate What Your Monthly Car Payment Will Be
Your payment depends on the loan amount, interest rate, and how many months you'll pay
Your monthly car payment is determined by three numbers: how much you're borrowing, the interest rate the lender charges, and the length of the loan in months. A $20,000 loan at 6% over 60 months costs less per month than the same loan over 36 months, but you pay more interest overall. A higher interest rate raises your monthly payment on any loan size. You can calculate your own payment before you walk into a dealership or apply for a loan, which gives you control over what you're willing to spend.
The math is straightforward once you know all three numbers. Lenders use a standard formula, and you can use the same one with a calculator, a spreadsheet, or an online payment calculator. Understanding how the numbers work together helps you see why a lower interest rate saves you money and why a longer loan term feels easier month-to-month but costs more in the end.
Key Takeaways
- Your payment is calculated from the loan amount, the interest rate, and the number of months you have to repay—you need all three to know your payment.
- A longer loan term (60 months instead of 48) lowers your monthly payment but increases the total interest you pay over the life of the loan.
- A 1% difference in interest rate can change your monthly payment by $15 to $30 on a typical car loan, so shopping for the best rate matters.
- You can calculate your payment yourself using an online calculator or a spreadsheet formula before you commit to a loan.
- Your actual payment may be higher if you add insurance, taxes, registration, or gap insurance to the financed amount.
The three numbers that set your payment
Loan amount is what you actually borrow. If the car costs $25,000 and you put down $5,000, you borrow $20,000. If you roll negative equity from a trade-in into the new loan, the amount you borrow goes up. This is the starting point for your payment calculation.
Interest rate is the percentage the lender charges you for borrowing. Rates vary by lender, your credit score, the age of the car, and the length of the loan. A rate of 4% means you pay 4% of the remaining balance each year as interest. On a $20,000 loan, that's roughly $800 in the first year, but the amount drops as you pay down the balance. A rate of 7% on the same loan costs roughly $1,400 in the first year.
Loan term is how many months you have to pay it back. Common terms are 36, 48, 60, and 72 months. A 60-month loan spreads the same amount of money over more payments, so each payment is smaller. A 36-month loan packs the same amount into fewer payments, so each one is larger. The trade-off is that the 60-month loan costs more in total interest because you're paying interest for longer.
How to calculate your payment yourself
The formula lenders use is: Monthly Payment = [P × (r × (1 + r)^n)] / [((1 + r)^n) − 1], where P is the loan amount, r is the monthly interest rate (annual rate divided by 12), and n is the number of months. You do not need to do this by hand. A spreadsheet like Google Sheets or Excel has a built-in function called PMT that does it for you in one line.
In Google Sheets, the formula looks like this: =PMT(rate, nper, pv). For a $20,000 loan at 6% annual interest over 60 months, you would enter: =PMT(0.06/12, 60, -20000). The result is your monthly payment before taxes and insurance. The negative sign in front of the loan amount tells the spreadsheet you are borrowing money, not lending it.
If you do not want to use a spreadsheet, dozens of free online car payment calculators exist. You enter the loan amount, the interest rate, and the number of months, and the calculator shows you the monthly payment instantly. This is faster than a spreadsheet if you only need one calculation, but a spreadsheet is better if you want to test different scenarios—what if the rate drops to 5%? What if you borrow $18,000 instead of $20,000?
How interest rate changes affect your payment
A 1% difference in interest rate does not sound like much, but it adds up quickly on a car loan. On a $20,000 loan over 60 months, the difference between 4% and 5% is about $18 per month, or roughly $1,080 over the life of the loan. The difference between 4% and 7% is about $50 per month, or roughly $3,000 total. This is why shopping around for the best rate—through your bank, a credit union, or multiple lenders—can save you hundreds of dollars.
Your interest rate depends on several things you can and cannot control. You cannot control the prime rate that the Federal Reserve sets, which affects what all lenders charge. You can control your credit score by paying bills on time and keeping credit card balances low, which usually lowers the rate you are offered. You can also control which lender you choose—credit unions often offer lower rates than dealership financing, and banks vary widely in what they charge.
How loan term length changes your payment and total cost
Stretching a loan over more months lowers your monthly payment but raises the total amount you pay in interest. Here is a real example: a $20,000 loan at 6% interest costs $386 per month over 60 months, or $23,160 total. The same loan over 72 months costs $319 per month, or $22,968 total—wait, that is less total? No. Over 72 months it costs $22,968, which is $1,968 in interest. Over 60 months it costs $23,160, which is $3,160 in interest. The 72-month loan saves you $50 per month but costs you $1,192 more in total interest.
The longer the term, the more interest you pay because you are borrowing the money for longer. A 48-month loan at 6% on $20,000 costs $469 per month and $22,512 total—$2,512 in interest. A 36-month loan costs $599 per month and $21,564 total—$1,564 in interest. If you can afford the higher monthly payment, a shorter term saves you thousands in interest. If you cannot, a longer term is a real option, but go in knowing it costs more.
What gets added to your payment in the real world
The payment you calculate is the principal and interest only. In reality, your monthly bill from the lender may include other costs. Sales tax on the car is often rolled into the loan, which increases the amount you borrow. Registration and title fees may also be financed. Gap insurance (which covers the difference between what you owe and what the car is worth if it is totaled) can be added to the loan. Extended warranties are sometimes financed too.
If you finance $22,000 instead of $20,000 because taxes and fees are included, your payment goes up by roughly $33 per month on a 60-month loan at 6%. Ask the lender or dealer for an itemized list of what is being financed before you sign. Some of these costs can be paid upfront instead of financed, which lowers your loan amount and your monthly payment.
Your actual monthly payment to the lender is just the loan payment. But your total monthly cost of owning the car also includes insurance, fuel, and maintenance. These are separate from the loan payment and vary based on the car, where you live, and how much you drive.
How to use payment calculations to make a decision
Before you go to a dealership or apply for a loan, calculate what payment you can actually afford. A common rule is that your car payment should not exceed 15% to 20% of your monthly take-home pay. If you take home $3,000 per month, a payment between $450 and $600 is reasonable. Use this as your ceiling, then work backward to see what loan amount and term make sense.
If you can afford $500 per month and you find a 6% interest rate, you can borrow about $24,000 over 60 months or about $18,000 over 36 months. Knowing this before you shop means you will not fall in love with a car you cannot afford, and you will know immediately whether a dealer's offer is realistic. You can also use payment calculations to compare different cars—a $22,000 car at 5% over 60 months costs less per month than a $25,000 car at the same rate and term.
Frequently Asked Questions
Does my credit score affect the interest rate I am offered?
Yes. Lenders use your credit score to decide how much risk you are, and they charge higher rates to borrowers with lower scores. A score above 750 typically gets the best rates. A score between 650 and 750 gets middle rates. A score below 650 usually gets higher rates or may be declined. You can request your credit report for free once per year at annualcreditreport.com to check for errors.
Can I pay off my car loan early without a penalty?
Most car loans allow you to pay early with no penalty, but check your loan agreement to be sure. Paying early saves you interest because you stop paying interest once the loan is gone. If you get a bonus or tax refund, putting it toward your car payment can shorten the loan by months and save hundreds in interest.
What is the difference between APR and interest rate?
The interest rate is the percentage you pay on the loan. APR (annual percentage rate) includes the interest rate plus other costs like origination fees, and it gives you a fuller picture of what the loan actually costs. Always compare APRs when shopping for loans, not just interest rates.
If I put down a larger down payment, how much does my monthly payment drop?
Every dollar you put down reduces the loan amount by one dollar, which lowers your payment proportionally. A $5,000 down payment instead of $3,000 reduces the loan by $2,000, which lowers your 60-month payment at 6% by about $39 per month. Putting down more upfront saves you money in interest and lowers your monthly obligation.
What happens to my payment if interest rates rise before I get approved?
If you have a pre-approval from a lender, the rate is usually locked for a set period—often 30 to 60 days. If rates rise after your pre-approval expires and before you finalize the loan, your rate may go up. This is why it is important to move quickly once you have a pre-approval and have found a car you want to buy.