Auto Loan Amortization Table Calculator and Guide

This auto loan amortization table calculator estimates a fixed-rate car loan’s monthly payment and total interest from the amount financed, APR, and term. Enter those three figures to see the payment and interest over the full term; the calculation uses the standard level-payment formula, while a full month-by-month table can be built from the same inputs.

Formula

The monthly payment is the amount that, when paid at the end of each month, repays the principal and interest over the selected number of payments. The standard formula is:

Payment = P × r ÷ [1 − (1 + r)⁻ⁿ]

• P is the loan principal, or amount financed, in dollars.
• r is the monthly interest rate, calculated as APR ÷ 1,200 when APR is entered as a percentage per year.
• n is the number of monthly payments, calculated as years × 12.

Total interest in this calculator is monthly payment × number of payments − principal. Its payment formula is shown before cent-rounding; the displayed payment is rounded to two decimal places. As a result, the displayed total-interest estimate can differ slightly from a lender’s schedule, which may use unrounded internal amounts, daily interest, or other contract-specific methods.

Worked Example

Using the calculator’s default inputs—$20,000 financed, 8% APR, and a five-year term—there are 5 × 12 = 60 monthly payments. The monthly rate is 8 ÷ 1,200 = 0.0066667.

Substitute those values into the payment formula:

Payment = 20,000 × 0.0066667 ÷ [1 − (1.0066667)⁻⁶⁰] ≈ $405.53 per month.

The calculator’s total-interest expression uses the displayed payment: $405.53 × 60 − $20,000 = $4,331.80. The corresponding total of the scheduled payments is $24,331.80. These figures are an estimate based on the inputs and assumptions below, not a lender’s payoff quote.

Assumptions

• The APR and payment amount are fixed throughout the term.
• Payments are monthly, made at the end of each period.
• Interest accrues monthly at APR ÷ 12, expressed as a decimal.
• The estimate excludes taxes, insurance, fees, optional products, and other costs unless they are included in the amount financed.

What an Auto Loan Amortization Table Shows

An amortization table—also called an amortization schedule—breaks each scheduled payment into principal and interest, then shows the remaining balance. At the beginning of a typical fixed-rate loan, the balance is relatively high, so more of each payment goes to interest. As principal is paid down, the interest portion generally falls and the principal portion rises. The monthly payment can remain level even though its parts change.

For a month-by-month schedule, calculate interest for each period as the balance at the start of the month multiplied by the monthly rate. Subtract that interest from the payment to find the principal paid. Then subtract the principal paid from the prior balance. For example, with the default inputs, the first month’s estimated interest is $20,000 × 0.0066667, or about $133.33; about $272.20 of the $405.53 payment goes to principal, leaving approximately $19,727.80. Small differences can arise from rounding.

How to Use the Estimate

1. Enter the amount financed, not automatically the car’s advertised price. The financed amount may reflect a down payment, trade-in, taxes, fees, or other items, depending on the contract.
2. Use the APR and term shown in the lender’s written offer or disclosure. Do not substitute a quoted interest rate if the APR is the figure being requested.
3. Read the monthly payment as the estimated scheduled loan payment, and total interest as the estimated cost of borrowing over all scheduled payments.
4. Compare the inputs and assumptions with the actual contract. A different amount financed, term, rate, payment date, or fee treatment changes the schedule.

The calculator is useful for understanding how loan size and term affect payment arithmetic, and for checking a payment estimate against the stated loan inputs. It does not determine what a household can afford, whether a lender will approve an application, or the complete cost of owning a vehicle. Vehicle expenses such as insurance, fuel, maintenance, and registration are outside the loan formula.

Common Misunderstandings and Limits

A common misconception is that the monthly payment alone reveals the total cost. A longer term can spread repayment across more months, which may lower the scheduled monthly payment while increasing the number of periods in which interest accrues. To understand the loan arithmetic, review the principal, APR, term, payment, and total interest together rather than treating one number as the whole picture.

APR is not the same as the monthly rate. For this standard estimate, divide the annual percentage by 12 and convert the percentage to a decimal: 8% becomes 0.08 ÷ 12, or 0.0066667 per month. Entering 8 as a monthly rate would be a major unit error. Also check whether the amount entered is the amount financed rather than the vehicle price before down payment or trade-in.

Actual contracts may calculate interest using daily balances, vary payment dates, include financed charges, or have a final payment that differs slightly because of rounding. Extra payments can also change the balance and payoff timing, but this calculator assumes only the scheduled level payment. It does not model late payments, skipped payments, refinancing, variable rates, or a lender’s payoff calculation. Ask the lender for contract-specific figures when precision matters.

Frequently Asked Questions

What is an auto loan amortization table?
An auto loan amortization table lists each scheduled payment and shows how much is allocated to interest and principal, along with the balance remaining after payment.

How do I calculate an auto loan monthly payment?
Convert APR to a monthly decimal rate by dividing it by 1,200, convert the term to months, then use the fixed-payment formula shown above with the amount financed as principal.

Why does the interest portion change if my payment stays the same?
Interest for each period is calculated on the outstanding balance. As scheduled principal payments reduce that balance, less interest accrues in later periods, so more of a level payment can go toward principal.

Does this calculator include a down payment or trade-in?
Not separately. Enter the amount actually financed after any down payment or trade-in adjustment, if the contract’s financed amount reflects those items.

Does paying extra change an amortization table?
Yes. An extra amount applied to principal can reduce the balance faster and change later interest and payoff timing. This calculator does not model extra payments; the contract and lender determine how payments are applied.

This result is an estimate, and the lender’s disclosure gives the exact figures.

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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