Which auto calculator do I need?
- Buying with a loan? The auto loan calculator gives the monthly payment and total interest after your down payment and trade-in.
- Offered a lease? Check the dealer’s numbers with the car lease calculator, which breaks the payment into depreciation, rent charge and tax and converts the money factor to an APR.
- Undecided? The lease vs. buy calculator compares net cost over the same period, crediting the buyer with the car’s remaining equity.
- Budgeting the long run? The car ownership cost calculator totals depreciation, fuel, insurance, maintenance, interest and fees per year, month and mile.
- Planning a drive? The gas cost calculator prices a trip’s fuel and splits it among passengers, and the MPG calculator measures your real fuel economy from a fill-up.
- Changing tires? The tire size calculator compares two sizes and shows the speedometer error.
Thinking about a car purchase in the right order
Most people start with the monthly payment, but the payment is the last number to look at, not the first. A sensible sequence starts with the budget. Decide what you can spend each month on everything a car costs, not only the loan or lease. Fuel, insurance, registration and upkeep are paid whether or not you have a loan, and for many households they add up to as much as the payment itself. The ownership cost calculator turns those pieces into a single monthly figure, which makes it easy to see whether a particular model really fits.
Next, compare how you will pay. Cash, a loan and a lease each move money at different times. Comparing them over one shared period, as the lease vs. buy tool does, keeps the comparison honest. Only after that should you negotiate a price and check the dealer’s figures, line by line, against the loan or lease calculator.
Running costs after you drive away
Fuel is the cost you notice most often because you pay it every week. Measuring your real miles per gallon from a couple of fill-ups gives you a far better planning number than the window sticker, and it is also an early warning system: a steady drop in economy can point to low tire pressure or a maintenance problem. Before a long drive, price the trip with your measured MPG and the fuel prices along the route, and you will know what to set aside or how to split costs with passengers.
Tires are another overlooked cost. Changing to a different size can alter ride, handling, fuel economy and the accuracy of the speedometer and odometer, so compare the old and new sizes before you buy and confirm fitment and load rating with a tire professional.
Questions to ask at the dealership
Bring your own numbers so you can check the paperwork rather than take it on trust. For a loan, ask for the out-the-door price, the APR, the term and every fee being financed. For a lease, ask for the capitalized cost, the residual percentage, the money factor, the acquisition and disposition fees, the yearly mileage allowance and the charge per extra mile, and how sales tax will be collected in your state. Write each figure down, enter it in the matching calculator before you sign, and question any payment that doesn’t line up with your result. A small gap is usually rounding; a large one often means an add-on product or a marked-up rate.
How we build these tools
Every result comes from a published formula that is explained on the calculator’s own page, along with worked examples whose numbers match what the calculator returns. Lease payments follow the standard depreciation-plus-rent-charge method with sales tax on each payment. Loans use standard amortization, and tire math uses exact metric-to-inch conversion. See our methodology for details. Results are estimates; confirm figures with your dealer, lender or tire professional before you sign.