Auto loan calculator
Turn a dealer quote into a real monthly payment — sales tax, fees, trade-in and rolled-over debt included.
Runs entirely in your browser. Nothing you enter is uploaded.
Written and maintained by ReadoutKit / Takashi Yamazaki
How this works
What you are actually financing
The number that decides your payment is not the sticker price. It is the amount financed, and it is built by adding everything the lender advances on your behalf and subtracting everything you hand over up front:
financed = price + sales tax + fees − cash down − (trade-in value − trade-in owed)
On the default deal above, a $42,000 car with an $8,000 trade-in is taxed on $34,000, which adds $2,380. Fees add $900, cash and trade take away $13,000, and $32,280 is what you borrow. The payment follows from that figure alone. This is why two quotes on the same car can differ by $80 a month without either rate changing: the fees and add-ons folded into the balance moved instead.
What the term costs you: 36 to 84 months
Same car, same rate, same money down. Only the number of payments moves.
| Term | Monthly payment | Total interest | Total paid |
|---|---|---|---|
| 36 months | $1,004 | $3,868 | $36,148 |
| 48 months | $780 | $5,184 | $37,464 |
| 60 months | $647 | $6,529 | $38,809 |
| 72 months | $558 | $7,905 | $40,185 |
| 84 months | $495 | $9,310 | $41,590 |
Going from 36 months to 84 cuts the payment in half — $1,004 down to $495 — and multiplies the interest by nearly two and a half, from $3,868 to $9,310. Each extra year is roughly $1,400 of interest on this loan, bought with about $127 a month of breathing room. That is a real trade, and for some budgets it is the right one. What makes long car loans different from long mortgages is the asset underneath: a house may appreciate, a car will not.
What your credit score is worth
Auto lending prices risk far more steeply than mortgage lending. The spread between the best and worst advertised rates is routinely ten points or more, on the same car.
| APR | Monthly payment | Total interest | Total paid |
|---|---|---|---|
| 3.0% | $580 | $2,522 | $34,802 |
| 5.0% | $609 | $4,270 | $36,550 |
| 7.5% | $647 | $6,529 | $38,809 |
| 10.0% | $686 | $8,871 | $41,151 |
| 13.0% | $734 | $11,788 | $44,068 |
| 16.0% | $785 | $14,819 | $47,099 |
Between 3% and 16% sits $205 a month and $12,297 of interest — more than a quarter of the car’s price, decided entirely by the paperwork. This is why getting a rate quote from your own bank or credit union before you visit the dealer is worth more than any negotiation over the sticker. It also gives you a number to hold the dealer’s financing against, which is the only way to tell whether their rate is a subsidy or a markup.
The down payment, priced
Everything else fixed at the defaults, with only the cash down changing.
| Cash down | Amount financed | Monthly payment | Total interest |
|---|---|---|---|
| $0 | $37,280 | $747 | $7,541 |
| $2,000 | $35,280 | $707 | $7,136 |
| $5,000 | $32,280 | $647 | $6,529 |
| $8,000 | $29,280 | $587 | $5,923 |
| $12,000 | $25,280 | $507 | $5,114 |
Each $1,000 of cash removes about $20 a month and $200 of interest over five years. Put differently, the money you put down “earns” your APR, tax-free and risk-free, for as long as the loan runs. The other reason to put money down is protective rather than arithmetical: it keeps the balance below the car’s resale value in the early years, which is what stops a write-off from turning into a debt on a car you no longer have.
Rolling old debt into a new car
If you owe more on your trade-in than it is worth, dealers will happily add the shortfall to the new loan. The table below starts from a trade-in that exactly clears its own loan, then rolls increasing amounts of leftover debt into the deal.
| Debt rolled in | Amount financed | Monthly payment | Total paid | Extra cost |
|---|---|---|---|---|
| $0 | $40,280 | $807 | $48,428 | $0 |
| $2,000 | $42,280 | $847 | $50,832 | $2,405 |
| $4,000 | $44,280 | $887 | $53,237 | $4,809 |
| $6,000 | $46,280 | $927 | $55,641 | $7,214 |
| $10,000 | $50,280 | $1,008 | $60,450 | $12,023 |
Rolling $10,000 forward costs $12,023 — the debt plus $2,023 of interest on a car you sold. It also starts the new loan roughly $10,000 underwater, so the same problem is likely to be waiting at the next trade-in, one size larger. Breaking the cycle usually means keeping the current car until the balance clears, which is unglamorous and much cheaper than any financing structure.
Working backwards from a budget
Most buyers arrive with a monthly figure rather than a price. This table inverts the calculation: what a given monthly payment buys at 7.5%, with the same $5,000 down, $8,000 trade-in and fees.
| Monthly budget | Over 36 months | Over 60 months | Over 84 months |
|---|---|---|---|
| $300 | $20,845 | $25,824 | $30,111 |
| $400 | $23,850 | $30,488 | $36,204 |
| $500 | $26,854 | $35,152 | $42,297 |
| $700 | $32,863 | $44,480 | $54,484 |
| $900 | $38,872 | $53,808 | $66,670 |
The columns show exactly how a payment-first conversation works in the seller’s favour: at $400 a month, agreeing to 84 months instead of 36 raises the car you can “afford” from $23,850 to $36,204. Nothing about your finances improved. Decide the price first, then pick the shortest term whose payment you can live with.
What this calculator leaves out on purpose
- Insurance, fuel and maintenance. These often exceed the loan payment over the life of the car, and they vary too much by driver and model to guess at.
- Add-on products. Extended warranties, gap cover and protection packages are usually financed alongside the car. Add them to the fees field if they are in your quote.
- Manufacturer subsidies. Promotional APRs and cash rebates are usually mutually exclusive. Model each one separately rather than assuming you get both.
- Depreciation. Any resale-value curve would be a guess dressed as a fact, so the tool shows what you owe and leaves what the car is worth to you.
Reading the result honestly
A car loan is the one large debt most people take on for an asset guaranteed to lose value. That does not make it a mistake — transport has worth that a balance sheet does not capture — but it does mean the shortest affordable term, the largest sensible deposit, and a rate you sourced yourself are almost always the right answers. Use this tool to compare quotes before you sign, then check the final figures against the credit agreement you are actually offered.
Common questions
- What is the monthly payment on a $42,000 car?
- With $5,000 down, an $8,000 trade-in, 7% sales tax and $900 of fees rolled in, you finance $32,280. At 7.5% over 60 months that is $647 a month, and $6,529 of interest over the five years. Stretch the same loan to 84 months and the payment drops to $495 while the interest rises to $9,310 — the term tables in this article price every option from 36 to 84 months.
- Why is the dealer’s payment higher than the one I calculated?
- Almost always because something was added to the amount financed that you did not include. Documentation fees, registration and title, an extended warranty, gap insurance, paint protection, and any negative equity from your old car are all rolled into the loan and all earn interest. Ask for the amount financed, not the monthly payment — it is the only figure the two of you can compare directly.
- Does a trade-in reduce the sales tax?
- In most US states, yes: tax is charged on the price minus the trade-in allowance, so an $8,000 trade-in on a $42,000 car at 7% saves $560 of tax on top of the $8,000 itself. A handful of states tax the full price, and consumption taxes outside the US — Japan’s 10% among them — generally apply to the whole vehicle price with no trade-in offset. Use the tax toggle to match your own rule; the two settings can differ by several hundred dollars.
- Is a 72- or 84-month car loan a bad idea?
- It is not automatically wrong, but it inverts the usual relationship between what you own and what you owe. On this loan, 84 months saves $152 a month against 60 and costs $2,781 more in interest. The bigger risk is timing: a car depreciates fastest in its first three years while a long loan repays principal slowly, so you can spend years owing more than the car is worth. If you sell or total it in that window, the shortfall is yours to pay.
- What happens if I still owe money on my trade-in?
- The shortfall does not disappear — it is added to the new loan and charged interest at the new rate. Rolling $6,000 of negative equity into this deal raises the payment from $807 to $927 and adds $7,214 to what you hand over in total. That $1,214 gap is the interest you pay on the old car after you no longer own it.
- Should I take the 0% financing or the cash rebate?
- Price both. A rebate reduces the amount financed permanently, while 0% only removes the interest on whatever you do finance. On a five-year loan, a $2,500 rebate combined with a 6% credit-union rate usually beats 0% on the full price, and the gap widens the more you put down. Run the rebate version with your own bank’s rate and compare the total paid, not the monthly payment.
- Does this calculator send my figures anywhere?
- No. Every number is calculated in JavaScript in your browser. Nothing is uploaded, stored, or logged, and the tool keeps working with your network connection switched off once the page has loaded — which also means you can safely run a dealer’s quote through it while sitting in the showroom.
Sources
The formulas and rates used by this tool come from the documents below. Rules change; when a figure here disagrees with the source, the source is right.
Figures checked against the sources below on September 17, 2026.
- Auto loans — understanding the total cost of your loanConsumer Financial Protection Bureau
- G.19 Consumer Credit — new car loan terms at commercial banksBoard of Governors of the Federal Reserve System