Total Car Cost With Interest: Calculate Your Loan Cost

Calculate the total car-loan cost with interest by entering the amount financed, APR, and loan term. The calculator returns the monthly payment and total interest; add the amount financed to total interest to get the total of scheduled loan payments.

Formula

The monthly payment uses the standard fixed-payment loan formula. Let P be the amount financed in dollars, APR be the annual percentage rate in percent, r be the monthly rate, and n be the number of monthly payments. Convert APR to a monthly decimal rate with r = APR / 1200, and convert years to payments with n = years × 12.

Monthly payment = P × r / [1 − (1 + r)⁻ⁿ]. The calculator rounds this payment to cents for display. Total interest = (rounded monthly payment × n) − P. The scheduled loan-payment total is therefore P + total interest, equivalently the rounded payment multiplied by n. This total is not necessarily the vehicle’s full ownership cost.

Worked Example

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

Monthly rate: r = 8 / 1200 = 0.0066667.
Number of payments: n = 5 × 12 = 60.
Payment before rounding: $20,000 × 0.0066667 / [1 − (1.0066667)⁻⁶⁰] ≈ $405.53, rounded to $405.53 per month.
Total of scheduled payments: $405.53 × 60 = $24,331.80.
Total interest: $24,331.80 − $20,000 = $4,331.80.

The displayed calculator outputs are a monthly payment of $405.53 and total interest of $4,331.80. Adding them gives scheduled payments of $24,331.80.

Assumptions

The APR and payment amount stay fixed throughout the term.
Payments are monthly and made at the end of each payment period, as in the standard amortizing-loan formula.
Interest accrues monthly at APR divided by 12; the formula uses APR / 1200 as a decimal monthly rate.
The calculation excludes fees, taxes, insurance, optional products, registration costs, and any down payment or trade-in unless those amounts are reflected in the amount financed.
The term is converted to a whole number of monthly payments by multiplying years by 12.

What the Total Includes—and Leaves Out

“Total car cost” can refer to more than one number. The calculator measures the total of scheduled principal-and-interest payments on the amount financed. It does not determine the vehicle’s out-the-door price or the cost of owning and operating it. To estimate the amount financed, start with the vehicle price and any costs included in the loan, then subtract any down payment, trade-in credit, or other amount paid upfront. Use the actual financed principal from the lender’s documents when available.

Insurance, fuel or charging, maintenance, repairs, parking, and recurring ownership charges are separate expenses. Sales taxes and fees may be paid upfront or included in the loan; if included, they increase the amount financed and therefore affect interest. A down payment reduces the loan principal, but it is still money spent on the car. For a broader cash-outlay estimate, add upfront payments and ownership expenses to the loan payments, taking care not to count a financed cost twice.

How APR and Loan Term Affect Cost

APR is entered as an annual percentage, while the formula uses a monthly decimal rate. For example, 8% becomes 0.08 per year and 0.08 / 12 per month, or 0.0066667. Do not enter 0.08 in the calculator’s percent field: that means 0.08%, not 8%. Use the APR and financed amount shown in the lender’s specific quote or disclosure; the default values are examples, not a prediction of an offered rate.

For a fixed principal and APR, a longer term generally spreads repayment across more installments and lowers the scheduled payment, but it also means interest accrues for more months. A shorter term generally has fewer payments and less time for interest to accrue, while its monthly payment is higher. The exact figures depend on the inputs and the rounded payment convention used here. Comparing terms means examining both the monthly payment and the full scheduled-payment total, not just one figure.

Common Calculation Mistakes and Limits

Using the sticker price instead of principal: The formula needs the amount actually borrowed, after upfront contributions and including any costs rolled into the loan.
Confusing APR with a monthly rate: Enter APR as a percentage per year; the calculator performs the monthly conversion.
Ignoring payment rounding: This calculator rounds the payment to cents and uses that rounded amount to calculate total interest. A lender’s final payment schedule can differ slightly because of payment dates, daily interest calculations, or a differently adjusted final installment.
Treating interest as every extra car expense: Interest is the borrowing cost in this model. It does not include insurance, fuel, maintenance, taxes paid outside the loan, or other ownership costs.
Assuming every contract is a level-payment loan: The formula is for a fixed-rate, fully amortizing loan with regular monthly payments. Variable rates, balloon payments, irregular payment timing, extra payments, and fees that change the effective borrowing cost are not modelled.

To check a real offer, confirm the amount financed, APR, number of payments, payment schedule, and any financed charges in the lender’s disclosure. The result is an estimate, and the lender’s disclosure gives the exact figures.

Frequently Asked Questions

How do I calculate the total amount paid for a car loan?
Multiply the monthly payment by the number of scheduled payments. With this calculator’s rounded-payment method, total interest is that payment total minus the amount financed.

Does total car cost with interest include my down payment?
No. The calculator totals payments on the loan only. Add a down payment separately to estimate the money paid toward the purchase, and avoid adding any amount twice if it was already included in the financed principal.

Why does a longer car loan usually cost more in interest?
With the same principal and APR, a longer term leaves the balance accruing interest over more payment periods. It can reduce the monthly payment while increasing the total scheduled interest.

Is APR the same as the monthly interest rate?
No. APR is entered as a yearly percentage. This formula converts it to a monthly rate by dividing the percentage by 1,200.

Does this calculator include taxes, insurance, or fees?
No. It calculates scheduled principal and interest only. Costs included in the amount financed affect the result through the principal, while costs paid separately must be considered outside the calculation.

Formula used

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

Each line is one input (in, sel, list) or one result (out: label, unit, formula, decimals). How the calculators work

Method: the standard loan formula for this calculation, fixed rate and monthly compounding unless stated, rounded as each result states. Not financial advice; no lender, rate or product is recommended. See formulas and assumptions, the disclaimer or report an error.