Car Loan Amortization Table Calculator and Guide

This car loan amortization table calculator estimates the monthly payment and total interest for a fixed-rate auto loan from its amount, APR, and term. Enter the figures from a lender’s loan disclosure or quote; the calculator returns a payment estimate and interest total, while the table method below shows how each payment is split between interest and principal.

Formula

The calculator uses the standard fixed-payment loan formula. It calculates the monthly payment from the principal, monthly interest rate, and number of monthly payments:

Payment = P × r ÷ [1 − (1 + r)⁻ⁿ]

• P is the amount financed, in dollars.
• r is the monthly interest rate as a decimal: APR ÷ 100 ÷ 12, or APR ÷ 1200.
• n is the total number of monthly payments: loan term in years × 12.

Total interest is estimated as monthly payment × n − P. The payment formula’s result is rounded to cents in the calculator display; the interest estimate uses that displayed monthly payment multiplied by the number of payments, then subtracts the principal. This is a level-payment estimate, not a schedule of lender-specific daily interest calculations.

Worked Example

Using the calculator’s default values—$20,000 financed, 8% APR, and a five-year term:

1. Convert the APR to a monthly decimal rate: 8 ÷ 1200 = 0.0066667.
2. Find the number of payments: 5 × 12 = 60.
3. Substitute into the payment formula: $20,000 × 0.0066667 ÷ [1 − (1.0066667)⁻⁶⁰].
4. The monthly payment is approximately $405.53 after rounding to cents.
5. Estimate total interest using the rounded payment: $405.53 × 60 − $20,000 = $4,331.80.

Because the payment is rounded to cents, a real final payment may differ slightly from the estimate. Lenders can also calculate interest and handle the final payment using their own contract terms.

Assumptions

• The interest rate is fixed for the full term.
• Payments are monthly, equal in amount, and made at the end of each payment period.
• Interest is modelled monthly at APR divided by 12.
• The calculation excludes fees, taxes, insurance, optional products, and any down payment or trade-in not already reflected in the amount financed.

How an Amortization Table Works

An amortization table, also called an amortization schedule, lays out a loan one payment period at a time. Each row typically shows the payment number, starting balance, payment, interest portion, principal portion, and remaining balance. The calculator above supplies the basic payment and total-interest figures; a full table requires applying the same monthly calculation repeatedly.

For each month, calculate interest as the balance at the start of the month multiplied by the monthly rate. Subtract that interest from the payment to get the amount applied to principal. Subtract the principal portion from the starting balance to find the next balance. In symbols:

• Interest for the period = starting balance × r.
• Principal repaid = payment − interest for the period.
• Ending balance = starting balance − principal repaid.

For example, on the first month of the default example, interest is about $133.33 ($20,000 × 0.0066667). Of the $405.53 payment, about $272.20 reduces principal, leaving an estimated $19,727.80 balance. In later months, the balance is lower, so the interest portion generally shrinks and the principal portion grows, although the scheduled payment stays level.

When to Use the Calculator and How to Read It

Use the estimate to understand how loan amount, APR, and term affect scheduled payments and interest under the stated assumptions. Enter the amount actually financed—not necessarily the vehicle’s advertised price—and use the APR and term specified in the lender’s quote or disclosure. If the quote includes products, taxes, or fees in the financed balance, those amounts affect the calculation when included in the loan amount.

The total-interest output represents the estimated interest over all scheduled payments, not the total amount paid. Adding the principal back gives the estimated total of payments: in the default example, $20,000 + $4,331.80 = $24,331.80. A longer term usually means more scheduled payment periods; whether the payment or total interest changes depends on the amount, rate, and term entered. The calculator does not decide whether a loan fits a person’s circumstances.

Limits, Rounding, and Common Mistakes

• Confusing APR with a monthly rate: Enter APR as a percentage per year, such as 8, not 0.08 or 0.6667. The calculator divides by 1200 internally.
• Using the wrong principal: The loan amount is the amount financed. A down payment or trade-in may reduce it; financed charges may increase it. Use the figure in the actual loan documents.
• Assuming all auto loans accrue interest identically: This calculator models monthly compounding at APR divided by 12. Some contracts may use a different interest-accrual method or payment timing, which can make actual amounts differ.
• Rounding every schedule row: Rounding monthly interest and balances to cents at each step can produce small differences from calculations that retain extra precision. A lender’s final payment can also be adjusted for rounding or timing.
• Treating the estimate as an all-in vehicle cost: The model excludes expenses not entered, such as insurance and taxes, and does not estimate operating costs or vehicle value.

For an accurate comparison of a quoted payment, check that the amount financed, APR, number of payments, and any included charges match the lender’s disclosure. This is estimate arithmetic for education, not financial advice. The result is an estimate, and the lender’s disclosure gives the exact figures.

Frequently Asked Questions

What does a car loan amortization table show?
It shows each scheduled payment and how much goes to interest and principal, along with the remaining balance after that payment.

How do I calculate the interest portion of a car payment?
For this monthly model, multiply the balance at the start of the period by the monthly rate (APR ÷ 1200). Subtract that interest from the payment to estimate the principal paid.

Why does the principal portion increase over time?
With a level payment and a declining balance, the interest charged each month generally falls. More of the same payment can then go toward principal.

Does this calculator include a down payment or trade-in?
Not as separate inputs. Reflect them in the loan amount: enter the amount financed after any down payment or trade-in credit, as shown in the quote or contract.

Why might my lender’s payment differ?
The contract may use different timing or interest calculations, include additional financed charges, or adjust the final payment. Compare the calculator inputs with the lender’s disclosure and use the disclosed figures for the contract amount.

Related

• Personal Loan Amortization Table Calculator
• Variable Rate Loan Amortization Table Calculator
• Home Loan Amortization Table: Payments and Balance

in p | Loan amount | $ | 20000 | 1 | 100000000
in apr | Interest rate (APR) | % | 8 | 0.01 | 100
in yrs | Loan term | years | 5 | 0.0833 | 50
out pmt | Monthly payment | $ | p * (apr / 1200) / (1 - (1 + apr / 1200) ^ -(yrs * 12)) | 2
out int | Total interest | $ | pmt * yrs * 12 - p | 2