Car Cost Comparison Calculator: Compare Monthly Costs

This car cost comparison calculator estimates the monthly cost of owning two vehicles using their purchase prices, down payments, loan terms, interest rates, and monthly running costs. Enter those figures for each car to compare loan payments, estimated ownership costs, and the difference between them.

Formula

The calculator first estimates the amount financed for each vehicle: loan principal P = vehicle price minus down payment. It then calculates the monthly payment for a fixed-rate, level-payment loan:

M = round(P × r / [1 − (1 + r)⁻ⁿ], 2)

Here, M is monthly loan payment in dollars, P is principal in dollars, r is monthly interest as a decimal (APR ÷ 1,200), and n is the number of monthly payments. Estimated monthly cost is M + C, where C is the monthly running-cost estimate in dollars. The final comparison is Car B’s estimated monthly cost minus Car A’s. A positive result means B’s estimated monthly cost is higher; a negative result means it is lower.

The running-cost input is a single estimate you supply. It can represent recurring expenses such as fuel, insurance, maintenance, repairs, registration, or parking, but it is not a quote or prediction. Avoid adding a cost twice if, for example, your estimate already combines several expense categories.

Worked Example

Using the calculator’s default values:

• Car A principal: $30,000 − $5,000 = $25,000. Car B principal: $35,000 − $5,000 = $30,000.
• Both APRs are 7%, so the monthly rate is 7 ÷ 1,200 = 0.0058333. Each term is 60 months.
• Car A payment: round($25,000 × 0.0058333 ÷ [1 − (1.0058333)⁻⁶⁰], 2) = $495.03.
• Car B payment: round($30,000 × 0.0058333 ÷ [1 − (1.0058333)⁻⁶⁰], 2) = $594.04.
• Car A estimated monthly cost: $495.03 + $400 = $895.03. Car B: $594.04 + $350 = $944.04.

The comparison is $944.04 − $895.03 = $49.01 per month. This is a comparison of the entered estimates, not a complete forecast of total ownership cost.

What to Include in a Car Cost Comparison

A monthly payment is only one part of owning a car. Running costs can differ substantially by vehicle and by how, where, and how much it is driven. For a more useful comparison, build each running-cost estimate from the same categories and time period.

• Fuel or charging: Estimate monthly use from expected distance and the vehicle’s energy consumption. Driving conditions and energy prices can change the result.
• Insurance: Use an actual quote for the vehicle and the intended driver when available; do not assume two cars cost the same to insure.
• Maintenance and repairs: Allow for routine service and less predictable repairs. A monthly average smooths expenses but does not mean bills arrive evenly.
• Other recurring costs: Consider registration, parking, tolls, and any other costs relevant to your situation.
• Up-front and end-of-loan costs: Down payment, taxes, fees, and the vehicle’s eventual resale value matter to a full ownership comparison, but are not included in the monthly-cost output.

How to Use the Results

Enter each vehicle’s price and down payment, then use the APR and term shown in the relevant lender disclosure or loan offer. Enter the monthly running-cost estimate separately. The calculator assumes that the amount financed is exactly price minus down payment; it does not add taxes or fees to the loan principal. If those costs are financed, include them in the price input only if doing so accurately represents the amount being financed, and keep the comparison consistent for both cars.

Change one assumption at a time to see what drives the difference. For example, a lower payment may result from a longer term, but the calculator’s monthly comparison does not show the full interest paid over the life of the loan. To assess the financed portion over the full term, multiply the rounded monthly payment by the number of payments; then subtract principal to estimate interest, subject to the loan’s actual terms and payment schedule.

Limits and Common Misconceptions

This is not a complete “total cost of ownership” calculator. It does not calculate depreciation, resale proceeds, sales taxes, loan fees, insurance premiums, fuel consumption, maintenance schedules, or future repair bills. Those amounts depend on vehicle details and circumstances that the inputs do not capture. It also assumes a fixed APR, monthly payments, and equal payments throughout the term.

One common misconception is that the car with the smaller monthly payment necessarily costs less. A longer repayment term can reduce the payment while increasing the number of payments and potentially the total interest. Another is that a higher-priced car must have the higher monthly ownership cost: a different down payment, APR, term, or running-cost estimate can change the comparison. Check the assumptions rather than treating the result as a recommendation.

Rounding is another source of small differences. Payments are rounded to cents before running costs are added. A lender’s precise payment can differ because the financed amount, fees, payment dates, interest calculation, or other contract details may not match this simplified model.

Frequently Asked Questions

What is included in a car’s monthly cost here?
The estimate adds the calculated loan payment to the monthly running-cost amount you enter. It does not automatically include insurance, fuel, maintenance, or other expenses; include the categories you want in that input.

Does this compare the total cost of two cars?
No. It compares estimated monthly loan payments plus entered monthly running costs. It excludes up-front costs, depreciation, resale value, and other unentered expenses.

Why can a more expensive car have a lower monthly payment?
The payment also depends on the down payment, APR, and loan term. A longer term or different financing assumptions can lower a monthly payment without making the vehicle less expensive overall.

Should I include insurance and fuel?
Include them in the monthly running-cost input if you want them reflected in the comparison. Use estimates specific to each vehicle, and make sure the same expense is not counted twice.

Why does my lender’s payment differ from this estimate?
The lender may use a different amount financed or account for fees, taxes, payment timing, or contract-specific calculations. Use the lender’s disclosed figures for the actual loan terms.

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in a | Car A price | $ | 30000 | 0 | 10000000
in ad | Car A down payment | $ | 5000 | 0 | 10000000
in ar | Car A APR | % | 7 | 0.01 | 100
in am | Car A loan term | months | 60 | 1 | 600
in ac | Car A monthly running costs | $ | 400 | 0 | 100000
in b | Car B price | $ | 35000 | 0 | 10000000
in bd | Car B down payment | $ | 5000 | 0 | 10000000
in br | Car B APR | % | 7 | 0.01 | 100
in bm | Car B loan term | months | 60 | 1 | 600
in bc | Car B monthly running costs | $ | 350 | 0 | 100000
out ap | Car A monthly loan payment | $ | round((a - ad) * (ar / 1200) / (1 - (1 + ar / 1200) ^ -am), 2) | 2
out at | Car A estimated monthly cost | $ | ap + ac | 2
out bp | Car B monthly loan payment | $ | round((b - bd) * (br / 1200) / (1 - (1 + br / 1200) ^ -bm), 2) | 2
out bt | Car B estimated monthly cost | $ | bp + bc | 2
out dif | Car B minus Car A per month | $ | bt - at | 2