Understanding Your Car Loan Amortization Schedule

What is an amortization schedule?

Amortization is the process of paying off an auto loan over time in installments. An amortization schedule is a chart or table that details each periodic payment, showing the amount applied to principal and interest, and the remaining balance.

In an amortizing loan, each monthly payment is split between principal and interest. Early in the loan term, a greater portion of each payment goes toward interest rather than principal. As the loan balance decreases, the interest portion of each payment decreases and the principal portion increases.

The standard amortization formula to calculate the fixed monthly payment is M = P x [r(1+r)^n] / [(1+r)^n - 1], where P is the loan amount, r is the monthly interest rate, and n is the number of payments.

Yes, you can create your own schedule using a spreadsheet or a calculator. You need the loan amount, the monthly interest rate (annual rate divided by 12), and the number of payments. Then, use the amortization formula to find the monthly payment, and for each month, calculate interest as the previous balance times the monthly rate, and principal as the payment minus interest. Subtract principal from the balance and repeat.

• Each row in an amortization schedule shows the payment number, payment amount, interest paid, principal paid, and remaining balance.
• The schedule is based on a fixed interest rate and equal monthly payments over the loan term.
• With the same monthly payment, the principal portion grows over time while the interest portion shrinks.

Sources: Consumer Financial Protection Bureau, Sunward Credit Union, Arbor Financial Credit Union

How to read an amortization schedule

An amortization schedule is typically arranged as a table with one row per payment. Columns include the payment number, the total payment amount, the interest paid, the principal paid, and the remaining balance after the payment.

The first row shows the initial loan amount as the starting balance. After each payment, the interest is calculated on the current balance, so the interest portion is highest at the beginning and decreases each month. The principal portion is the total payment minus the interest, so it increases over time.

• The "principal paid" column shows how much of that payment reduces your loan balance.
• The "interest paid" column shows the cost of borrowing for that month.
• The "remaining balance" column shows what you still owe after making the payment.
• You can see exactly when the balance will reach zero, which is the end of your loan term.

Sources: Consumer Financial Protection Bureau, Arbor Financial Credit Union

Sample amortization schedule

The following table is a sample amortization schedule for a $20,000 auto loan with a 5% annual interest rate and a 60-month term. The monthly payment is calculated using the standard formula. This example is for illustration; actual numbers may vary based on your loan terms.

Sources: Consumer Financial Protection Bureau, Sunward Credit Union

Principal vs interest: how the split changes

In the early years of an amortized auto loan, most of each payment goes toward interest. This is because the interest is calculated on the outstanding principal balance, which is highest at the start. As you pay down the principal, the interest charged each month decreases, allowing more of your payment to go toward principal.

For example, in the sample above, the first payment includes $83.33 in interest and $294.09 in principal. By the 24th month, interest drops to $50.18, and principal increases to $327.24. By the final payment, interest is just $1.54 and principal is $375.88.

This structure means the principal balance decreases slowly at first, then more quickly toward the end of the loan term.

Sources: Consumer Financial Protection Bureau, Sunward Credit Union, Arbor Financial Credit Union

Effect of extra payments on amortization

Making extra payments on your auto loan can reduce your principal faster and save on interest. When you make an extra payment, that amount goes directly toward the principal, reducing the balance before it can accrue more interest. This can shorten the loan term and reduce total interest paid.

The exact effect depends on the amount and timing of the extra payment. Making an extra payment early in the loan term reduces the principal while the balance is still high, which saves more interest compared to making the same extra payment later.

Sources: Sunward Credit Union

Using a calculator to create your own schedule

You can use an auto loan calculator to generate an amortization schedule for your specific loan. To get started, you need the loan amount, the annual interest rate, and the loan term in months. The calculator uses the standard amortization formula to determine your monthly payment and then breaks down each payment into principal and interest.

Many online calculators allow you to input these numbers and instantly see a full amortization table. You can also build your own schedule manually using a spreadsheet and the formula provided earlier. By doing so, you can explore different loan terms or interest rates and see how they affect your monthly payment and total interest.

• Input variables: loan amount, annual interest rate, loan term.
• The calculator outputs a monthly payment and a full schedule.
• You can adjust the term to see the trade-off: longer terms mean smaller monthly payments but more total interest paid.

Sources: Consumer Financial Protection Bureau, Sunward Credit Union