calculate-loan

01 Loan payments

Car Finance Affordability Calculator and Payment Guide

Calculator No. 01-7186 · Updated · Formula and assumptions shown below

Monthly payment $405.53
Total interest
$4,331.67
= Monthly payment × loan term × 12 − loan amount
Loan amount
$20,000
Input
Interest rate (APR)
8 %
Input
You enter
Loan amount ($), Interest rate (APR) (%), Loan term (years)
You get
Monthly payment ($), Total interest ($)
Rounding
2 dp

Estimate for education, not financial advice. The result follows from the numbers you enter and the formula shown. It is not a quote or an offer, and it does not include fees, taxes or insurance unless the calculator asks for them. Ask your lender for the exact figures.

This car finance affordability calculator estimates a fixed monthly payment and total interest from the amount borrowed, APR and loan term. Enter the figures supplied for your proposed finance; the results are arithmetic estimates, not an assessment of what you can afford or whether a lender will approve you.

Formula

The calculator uses the standard fixed-payment amortizing loan formula. Let P be the amount borrowed in dollars, a the annual percentage rate (APR) entered as a percentage, r = a / 1200 the monthly rate as a decimal, and n = 12 × y the number of monthly payments for a term of y years. The monthly payment is:

M = P × r / [1 − (1 + r)−n]

Total interest is calculated as I = M × n − P. The calculator rounds the payment to cents before using it to estimate total interest. It assumes the same payment is made each month and that the loan balance is repaid over the stated term.

Worked Example

Using the default inputs—loan amount $20,000, APR 8%, and term 5 years:

  1. Convert the APR to a monthly decimal rate: r = 8 / 1200 = 0.0066667.
  2. Convert the term to payments: n = 5 × 12 = 60.
  3. Substitute the values: M = 20,000 × 0.0066667 / [1 − (1.0066667)−60].
  4. Round the monthly payment to cents: $405.53 per month.
  5. Estimate interest using the rounded payment: I = $405.53 × 60 − $20,000 = $4,331.80.

Assumptions

  • The interest rate stays fixed for the full term.
  • Payments are equal monthly instalments and are made at the end of each payment period.
  • Interest accrues monthly at APR divided by 12.
  • The calculation excludes any fees, taxes, insurance, optional products, down payment and trade-in unless reflected in the amount borrowed.

What Affordability Means in Car Finance

“Car finance based on affordability” can refer to two different questions. A lender may assess information about an applicant and the proposed agreement before deciding whether to offer finance. Separately, a household can estimate whether the full cost of having a car fits its own budget. This calculator does neither assessment: it works out an estimated payment from the three entered loan figures.

A payment that looks manageable on its own does not capture the whole cost of a car. Budget planning may also need to account for fuel or charging, insurance, maintenance, repairs, parking and other transport costs. Those amounts vary by vehicle, usage and personal circumstances, so they are not built into the payment formula.

How the Estimate Relates to a Finance Offer

The amount financed is not necessarily the vehicle’s advertised price. A deposit or trade-in may reduce the amount borrowed, while items included in the finance agreement may increase it. Use the amount that the lender’s written quotation identifies as the amount financed, rather than assuming it equals the car’s price.

The APR and term also matter. With the same principal and APR, a longer term generally spreads repayment over more months and changes the monthly payment and total interest. It does not make the car itself cheaper, and a longer period can mean paying interest for longer. This calculator keeps the APR fixed and does not model a changing balance caused by irregular payments.

Actual agreements may include charges or features that this simple calculation does not represent. For an accurate comparison, check the lender’s disclosure for the amount financed, payment schedule, APR, total of payments, fees, any final or balloon payment, and conditions that affect the balance. Enter the quoted amount, rate and term to make an estimate; do not treat the output as a quote or approval decision.

Using the Result and Avoiding Misunderstandings

Change one input at a time to see how the estimate responds. For example, holding the amount and APR constant while changing the term isolates the effect of spreading payments across a different number of months. If a lender quotes a different monthly figure, first check whether the financed amount, APR, term, payment dates, fees or final payment differ from the calculator’s assumptions.

  • Use APR as a percentage, such as 8 for 8%, not as 0.08.
  • Enter the loan amount, not the monthly payment or total car price if a deposit reduces borrowing.
  • Check the term is in years, as requested. A 60-month term is 5 years.
  • Remember that rounding the monthly amount to cents can make the final payment differ slightly from a fully unrounded mathematical schedule.

The input range accepts APR values from 0.01% to 100% and terms from 0.0833 to 50 years. These are calculator limits, not statements about rates or terms available from any lender. A zero-interest loan is not accepted by this formula because its payment equation divides by the monthly rate; for a genuinely zero-interest agreement, payment arithmetic would simply be the amount borrowed divided by the number of payments, before any charges.

Frequently Asked Questions

Does car finance approval depend only on the monthly payment?
No. The calculator only estimates a payment. A lender makes its own decision using its processes and the details of the application and proposed agreement; this page does not model those decisions.

Does this calculator tell me how much car I can afford?
No. It calculates a payment from an amount, APR and term. It does not know your income, regular expenses, other commitments or running costs, so it cannot determine a personal budget or affordability.

Why is the lender’s payment different from this estimate?
The figures or assumptions may differ. Check the amount financed, APR, term, fees, payment dates and whether the agreement has a final payment or other features not represented here.

Does a longer car finance term reduce the total cost?
This calculator shows how a changed term affects an estimated payment and interest when the amount and APR are held constant. A longer term usually means more scheduled payments; compare the total amount payable in the actual disclosure rather than looking only at the monthly figure.

Are insurance, fuel and maintenance included?
No. The estimate covers principal and interest under its stated assumptions. Insurance, fuel or charging, servicing, repairs and other ownership expenses are separate.

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

Related

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.

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