Auto Loan Calculator With Amortization Table

An auto loan calculator with an amortization table estimates your monthly principal-and-interest payment and shows how each scheduled payment changes the balance. Enter the amount financed, APR, and term to calculate the payment and total interest; the table itself can be built from the same figures, as explained below.

Formula

The calculator uses the fixed-rate, level-payment loan formula. Monthly payment = P × r ÷ [1 − (1 + r)⁻ⁿ]. Here, P is the amount financed in dollars, r is the monthly interest rate as a decimal (APR ÷ 1,200), and n is the number of monthly payments (term in years × 12). Total interest is the rounded monthly payment multiplied by n, less P. The displayed payment is rounded to cents; the total-interest estimate uses that rounded payment.

An amortization table applies the same monthly rate and payment one period at a time. For month k, interest is the opening balance multiplied by r; principal paid is the payment minus that interest; closing balance is opening balance minus principal paid. The closing balance becomes the next month’s opening balance. Equivalently, before rounding adjustments, balance after k payments is P(1 + r)^k − PMT × [(1 + r)^k − 1] ÷ r. A real payment schedule may vary slightly because lenders calculate interest and handle cents according to their contract.

Worked Example

Using the calculator’s default inputs: P = $20,000, APR = 8%, and term = 5 years.

1. Monthly rate: r = 8 ÷ 1,200 = 0.0066667.
2. Number of payments: n = 5 × 12 = 60.
3. Payment: $20,000 × 0.0066667 ÷ [1 − (1.0066667)⁻⁶⁰] = approximately $405.53 per month.
4. Total of scheduled payments: $405.53 × 60 = $24,331.80.
5. Estimated total interest: $24,331.80 − $20,000 = $4,331.80.

The first amortization row illustrates the split: interest is $20,000 × 0.0066667, or about $133.33; principal is $405.53 − $133.33, or $272.20; and the estimated balance after payment one is $19,727.80. Later rows recalculate interest from the lower balance. The last payment may need a small adjustment to clear the remaining balance exactly.

Assumptions

• The APR stays fixed for the entire term.
• Payments are made monthly at the end of each period; the first payment is one month after the loan begins.
• Interest is modelled monthly at APR ÷ 12, with no daily-interest timing adjustments.
• The calculation excludes fees, taxes, insurance, add-on products, and any separate down payment or trade-in unless those amounts have already been reflected in the amount financed.

How to Read an Amortization Table

A complete schedule usually has columns for payment number or date, opening balance, payment, interest, principal, and closing balance. In the early rows, the outstanding balance is larger, so the interest portion is usually larger. As principal is repaid, interest for later periods declines and more of a level payment goes toward principal. This is why the monthly payment can stay constant while its components change.

For each row, check that interest plus principal equals the scheduled payment, subject to rounding. The closing balance should generally fall after each payment and reach approximately zero at the end. If a table is displayed to cents, its row totals can differ by a few cents from a calculation performed with unrounded values. Lenders may also adjust the final payment or use a different interest-accrual convention.

What to Enter and What the Estimate Leaves Out

Use the amount actually financed rather than assuming it equals the vehicle’s advertised price. A down payment or trade-in can reduce the amount borrowed; taxes, fees, and optional products may increase it if they are included in the contract. The calculator does not determine which items belong in a particular contract. Get the amount financed, APR, payment frequency, and term from the lender’s written figures.

APR is entered as a yearly percentage, not as a monthly percentage. The formula divides it by 1,200 to get a monthly decimal rate. For example, 8% becomes 0.0066667 per month; entering 0.67 as the APR would mean 0.67% annually, not 8%. The term here is in years, and the formula converts it to months. A 60-month term is five years.

The calculation is an estimate of scheduled principal and interest, not a complete ownership budget or payoff quote. It does not include insurance, fuel, maintenance, registration costs, or costs that may be financed separately. It also does not model extra payments, skipped or late payments, a changing rate, or a contract-specific payoff amount. For a table that includes those details, use the actual contract terms and any lender-provided schedule.

Common Mistakes and Comparisons

• Confusing vehicle price with loan principal: the financed balance can differ after down payment, trade-in, and amounts added to the contract.
• Comparing payments alone: a longer term can reduce the scheduled monthly payment while increasing the number of payments and potentially total interest. Compare the term and total repayment alongside the payment.
• Treating APR as the monthly rate: the formula requires APR divided by 12 for a percentage rate, then expressed as a decimal; dividing by 1,200 does both conversions.
• Assuming the table is a payoff quote: exact payoff figures may depend on payment dates, accrued interest, and contract terms not represented here.

To compare two scenarios neutrally, enter each scenario’s actual amount financed, APR, and term separately, then examine both monthly payment and estimated total interest. Keep the principal and other assumptions consistent when you want to isolate the effect of changing one input. The calculator does not account for lender-specific fees or offer terms, so obtain those figures directly from the lender.

Frequently Asked Questions

How do I calculate an auto loan payment?
Convert APR to a monthly decimal by dividing by 1,200, convert the term to total months, and apply the fixed-payment formula shown above. This calculator performs those steps and rounds the payment to cents.

How do I make an auto loan amortization table?
For every month, multiply the opening balance by the monthly rate to find interest. Subtract that interest from the payment to find principal repaid, then subtract principal from the opening balance to get the closing balance.

Does the first payment mostly go to interest?
The split depends on the balance, monthly rate, and payment. Interest is calculated on the outstanding balance, so its share is generally larger earlier in a fixed-payment schedule and declines as the balance falls.

Why does my lender’s payment differ from the calculator?
Possible causes include a different amount financed, APR, term, payment date, fees, interest-accrual method, or rounding convention. Compare the inputs with the contract and ask the lender how its payment was calculated.

Does an amortization table show the exact payoff amount?
No. It estimates scheduled balances under the stated assumptions. A payoff figure can reflect accrued interest through a specific date and contract details not included in this calculation; request an exact figure from the lender.

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

Related

• Car Loan Calculator With Down Payment: Monthly Car Payment
• Auto Loan Calculator With Trade-In and Amount Owed (Negative Equity)

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