Which Calculator Do You Need?
Car financing decisions fall into a handful of distinct situations. Use the guide below to pick the right calculator before you run any numbers.
Buying a car with a loan
Use the Auto Loan Calculator to estimate your monthly payment from vehicle price, down payment, APR, and loan term. It also shows a full amortization schedule so you can see exactly how much of each payment goes to principal versus interest.
Leasing a car
Use the Auto Lease Calculator to convert MSRP, residual value, and money factor into a monthly payment. Lease math is opaque — dealers rarely show how the payment is derived. This calculator makes every component visible.
Deciding whether to lease or buy
Use the Lease vs. Buy Calculator to compare the total net cost of both options side by side. It accounts for the residual value you keep when you own, the down payments, and the cumulative monthly payments over any term you choose.
Trading in a car you still owe on
Use the Negative Equity Calculator to check whether you owe more than your car is worth — and to see what rolling that shortfall into a new loan actually costs. Going in without this number is one of the most common and expensive mistakes car buyers make.
Lowering your rate on an existing loan
Use the Auto Refinance Calculator to compare your current payment against a new rate. Even dropping from 8% to 6.5% on a $25,000 balance saves over $900 in total interest — worth checking if your credit has improved since you originally financed.
How Auto Loan Payments Are Calculated
Every monthly auto loan payment is determined by three inputs: principal (what you borrow), APR (the annual interest rate), and term (the number of months). The formula compounds monthly interest on the declining balance, which is why early payments are mostly interest and later payments are mostly principal.
Principal
Vehicle price minus your down payment and trade-in value. A larger down payment reduces the principal, cuts total interest, and lowers your monthly payment. Putting 15–20% down also protects you from negative equity — a situation where you owe more than the car is worth — which happens quickly on a vehicle depreciating 15–20% in its first year.
APR
Annual percentage rate — the interest rate plus any lender fees expressed as a yearly cost. Your APR depends on your credit score, loan term, and whether the vehicle is new or used. As of 2026, borrowers with strong credit (720+) typically qualify for 5–7% on new vehicles; used vehicle rates run 1–3 points higher. Get preapproved by at least two lenders before visiting a dealer — it gives you leverage on both the rate and the vehicle price.
Term
Loan terms run from 24 to 84 months. Longer terms lower the monthly payment but dramatically increase total interest paid — and keep you underwater for longer as the car depreciates. On a $30,000 loan at 7%, extending from 60 to 72 months saves about $75 per month but costs an extra $1,100 in total interest. Most financial advisors recommend 48–60 months as the practical ceiling.
Leasing vs. Buying: The Core Trade-Off
Leasing typically produces a lower monthly payment than financing the same vehicle, because you pay for depreciation rather than the full purchase price. The trade-off: you never build equity, you face mileage limits, and you're back to a payment when the lease ends. Buying costs more per month but results in a paid-off asset — one you can trade in, sell, or continue driving without a payment.
The decision usually comes down to how you use a car. If you drive under 12,000 miles per year, prefer driving a new vehicle every 2–3 years, and don't mind always having a payment, leasing can make sense. If you drive heavily, keep vehicles long-term, or want to own outright, buying is almost always cheaper in total. Use the Lease vs. Buy Calculator to run your specific numbers — the difference is rarely obvious without the math.
Frequently Asked Questions
What credit score do I need for a car loan?
Most lenders approve auto loans for borrowers with scores of 600 or above, but the best rates go to scores of 720 and higher. Below 600, you'll likely still find financing — but at significantly higher rates that add thousands in total interest. Check your credit report before applying and dispute any errors, since even a small score improvement can meaningfully lower your rate.
How much should I put down on a car?
A common guideline is 15–20% of the vehicle's price. On a $35,000 car, that's $5,250–$7,000 down. A larger down payment reduces your monthly payment, cuts total interest, and prevents negative equity. If you're financing a used vehicle that depreciates quickly, a bigger down payment is especially important.
Can I negotiate a car lease payment?
Yes. The capitalized cost (the effective selling price of the vehicle) is negotiable, just like a purchase price. Reducing the cap cost by $1,000 lowers your monthly payment by roughly $28 on a 36-month lease. The money factor (the lease's interest rate) is also sometimes negotiable, though dealers rarely volunteer that. Use the Lease Calculator to see exactly how cap cost and money factor changes affect your payment.
When does refinancing an auto loan make sense?
Refinancing makes sense when your credit score has improved since you took out the original loan, when market rates have dropped, or when you financed through a dealer at a marked-up rate. It generally doesn't make sense if you're near the end of your loan term (most interest is already paid) or if the vehicle is old enough that lenders won't refinance it. Use the Refinance Calculator to see if the monthly savings justify the process.
What is negative equity and how do I avoid it?
Negative equity (being "upside-down") means you owe more on your loan than the vehicle is currently worth. It happens when you finance a long-term loan on a vehicle that depreciates faster than you pay down the principal — common with 72- and 84-month loans or minimal down payments. Avoid it by putting 15–20% down, keeping loan terms to 60 months or fewer, and using the Negative Equity Calculator before trading in your current vehicle.