Used Car Weekly Payments Calculator and Loan Costs

This used car weekly payment calculator estimates the weekly amount for a fixed-rate auto loan from the amount financed, annual percentage rate (APR), and loan term. Enter the figures from a lender’s written quote to see the estimated weekly payment and total interest; the result is an arithmetic estimate, not an offer or approval decision.

Formula

The calculator first finds a level monthly payment using the standard fixed-rate loan formula, then converts that amount to an annualized weekly equivalent:

Monthly payment = P × r ÷ [1 − (1 + r)⁻ⁿ]
Weekly equivalent = monthly payment × 12 ÷ 52
Total interest = monthly payment × n − P

• P is the amount financed, in dollars. It is the loan principal after any down payment or trade-in credit and after any items added to the loan.
• r is the monthly interest rate as a decimal: APR ÷ 1,200. For an 8% APR, r is 0.0066667.
• n is the number of monthly payments: loan term in years × 12.
• 12 ÷ 52 converts the calculated annual sum of monthly payments into a weekly equivalent. It does not change the lender’s actual payment schedule.

The calculation assumes monthly payments. It does not calculate a contract with payments actually collected each week. A lender may use a different schedule or payment timing, so compare the calculator’s estimate with the payment frequency and amount stated in the loan documents.

Worked Example

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

Monthly payment = 20,000 × 0.0066667 ÷ [1 − (1 + 0.0066667)⁻⁶⁰] = $405.53 when rounded to cents.

Weekly equivalent = $405.53 × 12 ÷ 52 = $93.58. Total interest = $405.53 × 60 − $20,000 = $4,331.80.

These outputs describe the formula’s estimate. Because the calculator uses a rounded monthly payment to estimate total interest, a lender’s final schedule can differ by a small amount, particularly due to its payment dates and rounding rules.

Assumptions

• The APR is fixed for the full term and is entered as a yearly percentage.
• Payments are assumed to be equal monthly payments, with the first payment one month after the loan begins.
• Interest is modelled monthly at APR divided by 12.
• The calculation excludes taxes, registration charges, insurance, lender fees, optional products, and other costs unless they are already included in the amount financed.
• The weekly figure is an equivalent budget comparison, not a promise that the loan can be paid weekly or that weekly payments reduce interest.

What “Weekly Payments” Means

Car advertisements may show a weekly amount because it can be easier to compare with a weekly paycheque or household budget. That figure alone does not tell you the total cost. A smaller weekly number could result from borrowing less, paying over a longer period, or using a different APR. Compare the amount financed, APR, term, required payment schedule, and total of payments together.

There are 52 weeks in a year and 12 months, so converting a monthly payment to a weekly equivalent uses 12 ÷ 52—not simply dividing by four. For example, a $405.53 monthly payment corresponds to about $93.58 per week on an annualized basis. Paying $93.58 every week, however, produces 52 actual payments a year; that is not identical to making 12 monthly payments. Ask the lender how it applies extra or more frequent payments and whether the contract permits them.

What to Enter and How to Compare Quotes

• Amount financed: Use the loan principal, not necessarily the advertised vehicle price. A down payment or trade-in may reduce it; taxes, fees, or optional items may increase it if financed.
• APR: Enter the APR shown in the specific written quote. Do not substitute a promotional rate or an estimate from an advertisement.
• Term: Enter the full repayment term in years. If the agreement gives months, divide by 12; for example, 48 months is four years.
• Payment frequency: Check whether the lender quotes monthly, biweekly, or weekly payments. Use the calculator’s weekly equivalent only as a comparison when the loan itself is paid monthly.

For a meaningful comparison, hold the amount financed constant where possible and examine how changing the term affects both the periodic payment and total interest. A longer term generally spreads repayment across more payments in this formula, which can lower each scheduled payment while increasing the number of months over which interest accrues. The actual result depends on the entered APR, principal, and contract terms.

Common Problems and Costs to Check

A weekly payment quoted without the full loan details can obscure the total obligation. Ask for the amount financed, APR, term, payment frequency, and total scheduled payments in writing. Also check whether a deposit, trade-in value, final lump-sum payment, or optional product changes the advertised calculation. This calculator models an ordinary fully amortizing loan with equal payments and no final balloon amount.

Used-car condition is a separate cost consideration. The loan payment does not cover repairs, maintenance, fuel, insurance, or the possibility that the car needs work during the repayment term. Review the vehicle’s history and condition independently, and make sure the sales paperwork and financing figures refer to the same vehicle and transaction. The calculator cannot evaluate the vehicle, predict repair costs, or confirm the details of a contract.

Frequently Asked Questions

How do I calculate weekly payments on a used car?
For a monthly-payment loan, calculate the fixed monthly payment from principal, APR, and term, then multiply by 12 and divide by 52 for an annualized weekly equivalent. The calculator performs those steps.

Is a weekly payment the same as paying every week?
No. A weekly equivalent translates a monthly amount for comparison. If payments are actually collected weekly, the schedule and interest calculation may differ; check the contract for the exact payment amount and timing.

Does the weekly amount include insurance and fees?
Not by default. This estimate includes only the loan principal and interest implied by the APR and term. Costs may be included only if they are part of the amount financed, and separate ownership expenses are not calculated.

Why can two used-car offers have the same weekly payment but different costs?
The amount financed, APR, term, fees, and any final payment can differ. Compare the complete written figures and total payments rather than relying on the weekly amount alone.

Can I use the calculator for a weekly-payment loan?
Use it as a rough comparison only if the contract has monthly payments. A loan that truly requires weekly payments needs its own schedule and payment-frequency assumptions; use the lender’s disclosed figures for the exact amount.

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

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in p | Amount financed | $ | 20000 | 1 | 100000000
in apr | Interest rate (APR) | % | 8 | 0.01 | 100
in yrs | Loan term | years | 5 | 0.0833 | 50
out wk | Weekly payment | $ | (p * (apr / 1200) / (1 - (1 + apr / 1200) ^ -(yrs * 12))) * 12 / 52 | 2
out mp | Monthly payment equivalent | $ | p * (apr / 1200) / (1 - (1 + apr / 1200) ^ -(yrs * 12)) | 2
out ti | Total interest | $ | mp * yrs * 12 - p | 2