Auto Loan Calculator

What Is an Auto Loan?

Almost every car sold on finance in the United States is sold on the same instrument: a fixed-rate, fully amortizing, closed-end installment contract secured by the vehicle. The words below are the ones that appear on the paperwork, and knowing which figure each refers to is most of what separates a confident buyer from a nervous one.

The concept, plainly

Secured means the car is the collateral. The lender records a lien against the title, so the title is not fully yours until the final payment clears; miss enough payments and the lender can repossess the vehicle and pursue any shortfall between what it sells for and what you owe. That security is why auto rates sit well below credit-card rates for the same borrower.

Fully amortizing means every payment is identical and the balance reaches exactly zero on the last one — there is no balloon at the end. Each payment is split: interest is taken first, and the remainder reduces principal. Because interest is charged on the outstanding balance, the interest slice shrinks and the principal slice grows every month, which is why a loan balance falls slowly at the start and quickly at the end.

There are two ways to get the money. Direct lending means you arrange the loan yourself with a bank or credit union and walk in with a check. Indirect, or dealer-arranged, financing means the dealer submits your application to lenders, receives a wholesale rate back, and may add a markup before quoting you. Neither is automatically cheaper, which is the whole argument for arriving with a pre-qualified number in hand: it turns the finance office from a monopoly into a competitor.

APR, the amount financed, and what the numbers mean

The APR is an annualized cost of credit. The Consumer Financial Protection Bureau draws the distinction cleanly: the interest rate is what you pay the lender for borrowing the money, while the APR is that rate plus the additional fees charged with the loan. On a clean auto loan with no financed fees the two are the same number, which is why this calculator applies whatever you type as a monthly rate of APR ÷ 12. If your contract finances a fee, the true APR is higher than the note rate, and the figure to compare between offers is always the APR.

The amount financed is the balance interest is charged on — not the sticker price. It is the price plus taxes and any financed fees, minus your cash down and the trade-in allowance. Two buyers with the same $30,000 car can finance $22,800 or $31,980 depending on what they put in and what gets rolled in, and every downstream number follows from that one figure.

The term is stated in months, and it is the most manipulable number in the deal. A payment target can always be hit by adding months, so a payment quoted without a term attached tells you nothing at all. The finance charge is the total interest — what the loan costs you in dollars — and it is the line a longer term makes worse while making the payment look better.

The six figures this calculator asks for

Each field maps to a line on a real purchase order:

• Vehicle Price — the negotiated price of the car before tax, not the advertised MSRP. If you already know the destination charge and dealer fees, add them here; they are financed exactly the way the car is.
• Down Payment ($) — cash you hand over at signing. Enter 0 for none. Typing $3,000 with the dollar sign and comma is fine; the field strips anything that is not a digit or a decimal point.
• Trade-In Value ($) — the allowance the dealer credits for your old car, net of any loan payoff still owed on it. Enter 0 if you are not trading.
• Sales Tax Rate (%) — your combined state and local vehicle tax rate as a percentage. Leave it blank or enter 0 and no tax is added, which is what you want in a state with no vehicle sales tax or when you are paying the tax separately in cash.
• APR (%) — the annual percentage rate from your own pre-qualification or the dealer's quote. Anything from 0 to 40 is accepted; 0 models a manufacturer promotional rate.
• Loan Term — 36, 48, 60, 72 or 84 months. These five cover the overwhelming majority of retail contracts.

Get any one of these wrong and the payment is wrong in a predictable direction: an optimistic APR understates it, a forgotten tax line understates it, and a trade-in figure quoted before the payoff on your old car is deducted understates it badly.

How Do You Calculate an Auto Loan Payment?

Two steps, in this order: build the amount financed the way the dealer builds it, then amortize that balance over the term. Doing it the other way round — amortizing the sticker price and adding tax afterwards — is the most common way a hand calculation lands hundreds of dollars off.

The auto loan formula

Sales tax   = (price − trade-in) × tax rate ÷ 100
Financed    = price + sales tax − down payment − trade-in

r = APR ÷ 1200          (the monthly rate)
n = term in months

Payment = Financed × r ÷ (1 − (1 + r)⁻ⁿ)

Total interest = (Payment × n) − Financed
All-in cash    = (Payment × n) + down payment

• Financed — the balance interest is charged on, after tax is added and your cash and trade are taken off.
• r — the monthly rate. A 7% APR gives r = 7 ÷ 1200 = 0.00583333.
• n — the number of monthly payments: 36, 48, 60, 72 or 84.
• (1 + r)⁻ⁿ — the present-value factor that makes the final payment land exactly on zero.
• All-in cash — every dollar that leaves your hands, so the down payment is added back. It excludes the trade-in vehicle you handed over, because that was not cash.

When the APR is 0 the amortization term collapses and the payment is simply the financed amount divided by the number of months, which is why a 0% promotion produces suspiciously round figures.

Step by step

Using a $30,000 car with $3,000 down, no trade-in, a 6% vehicle tax rate, a 7% APR and a 60-month term:

• Step 1 — Find the taxable amount. There is no trade-in here, so the full $30,000 is taxed.
• Step 2 — Apply the tax rate: $30,000 × 6% = $1,800.
• Step 3 — Build the amount financed: $30,000 + $1,800 − $3,000 = $28,800.
• Step 4 — Convert the APR to a monthly rate: 7 ÷ 1200 = 0.00583333.
• Step 5 — Amortize: $28,800 × 0.00583333 ÷ (1 − 1.00583333⁻⁶⁰) = $570.27.
• Step 6 — Total the interest: ($570.27 × 60) − $28,800 = $5,416.
• Step 7 — Add your cash back for the all-in cost: ($570.27 × 60) + $3,000 = $37,216.

Step 3 is where hand calculations usually go wrong. Tax is financed along with the car unless you pay it separately at the counter, so it earns interest for the whole term exactly as the vehicle does.

Worked example: a $30,000 car at 7% for five years

Those inputs produce the following, straight from this page's formula:

$30,000 price · $3,000 down · no trade · 6% tax · 7% APR · 60 months

$570.27/month · $28,800 financed · $5,416 total interest · $37,216 all-in cash

Read the first payment to see how amortization actually behaves. Interest for month one is $28,800 × 0.00583333 = $168.00, so of the $570.27 you send, $402.27 reduces the balance. Just under 30% of that first payment is rent on the money; by the final payment almost none of it is.

Now look at the totals. The $5,416 of interest is 18.1% of the car's price, and the all-in cash cost of $37,216 is 24.1% more than the $30,000 on the windshield. Five years of financing at a mid-range rate adds roughly a quarter to the price of the car, and that is the figure the monthly-payment conversation is structured to keep out of view.

Five deals compared

Different shapes of transaction, all run through the same formula:

The used-car row is the one worth sitting with. An $18,000 car at 11% over five years generates $5,256 of interest — 29.2% of its price, and within $160 of the interest on a $30,000 car at 7%. Rate and term, not price, decide what the financing costs.

Sales Tax and Trade-Ins: What You Actually Finance

The amount financed is the only input the payment really cares about, and three things move it: the tax rule your state uses, how much cash you put down, and whatever the finance office manages to roll into the contract.

Why a trade-in is worth more than its trade-in value

In most states, vehicle sales tax is charged on the price after the trade-in allowance is deducted. The Texas Comptroller's motor vehicle tax guide states the rule and works an example: a purchaser who buys a $25,000 vehicle and trades in a $10,000 vehicle owes motor vehicle tax on the $15,000 difference. New York applies the same principle where the seller intends to resell the trade-in.

That credit is real money, and it is why trading a car in can beat selling it privately for an identical amount. Take the $30,000 car with $3,000 cash down at 7% over 60 months, and suppose the old car is worth exactly $5,000 either way. Traded in at a 6% tax rate, the taxable amount falls to $25,000, tax is $1,500, the amount financed is $23,500 and the payment is $465.33 with $4,420 of interest. Sold privately instead, with the $5,000 added to the cash down payment, tax is charged on the full $30,000 — $1,800 — so the amount financed is $23,800 and the payment is $471.27 with $4,476 of interest.

Net it out and the trade-in path costs $356 less over the five years: $300 of tax that is never charged, plus $56 of interest never paid on it. A private sale has to beat the dealer's offer by more than that before it is ahead, and that is before counting the afternoons spent meeting strangers in parking lots.

A minority of states give no trade-in credit at all. California's tax guide for motor vehicle dealers is explicit that the allowance for a trade-in cannot be deducted, so a $20,000 car sold with a $4,000 trade-in credit is taxed on the full $20,000. In one of those states, do not use the Trade-In field: leave it at 0 and add the trade allowance to your Down Payment instead. Tax is then charged on the full price, the trade still reduces what you borrow, and the arithmetic matches your paperwork.

City and county add-ons are often the difference between a 6% and a 9% rate, so pin down the combined figure before you type it in with the Sales Tax Calculator.

You pay interest on the tax, too

Unless you settle it in cash at the counter, the tax is financed with the car. Same $30,000 vehicle, $3,000 down, 7% APR and 60-month term, with only the tax rate changing:

Between a no-tax jurisdiction and a 9.5% one the payment moves $56.44 a month. Across the full term that is $3,386 more paid, of which $2,850 is tax and $536 is interest charged on the tax. Paying the tax at signing rather than financing it saves that $536 outright, which is the cheapest $536 available anywhere in the transaction.

What each $1,000 of down payment buys

Holding the $30,000 car, 6% tax, 7% APR and 60-month term fixed and moving only the cash down:

The relationship is linear: at 7% over 60 months, every extra $1,000 down removes $19.80 from the monthly payment and $188 from the total interest. A 20% down payment on this car — $6,000 — takes the payment from $629.68 to $510.87 and cuts $1,129 of interest.

There is a second effect the table cannot show. The down payment sets your loan-to-value ratio, which the CFPB defines as the loan amount divided by the vehicle's actual cash value, noting that the higher the LTV, the riskier the loan is to the lender. Lenders price that risk. Two buyers with identical credit can be quoted different rates purely because one is borrowing 130% of the car's value and the other 80%, so a larger down payment can improve the APR as well as shrink the balance — and those two effects compound.

What happens when things get rolled in

Two items commonly join the amount financed after the price is agreed: the unpaid balance on a trade-in worth less than its loan, and the finance office's add-on products. Both are nearly invisible in a monthly payment and expensive in total.

Say the finance office sells $2,500 of add-ons — a service contract, paint protection, a security etch. Enter $32,500 rather than $30,000 as the price and the payment goes from $570.27 to $622.75, while the all-in cash cost rises from $37,216 to $40,365. That is $3,149 for $2,500 of products, because the extras attract tax and then pay interest for five years. The CFPB's list of what is negotiable in a car deal includes add-on products and services explicitly, alongside the APR, the term, prepayment penalties, the trade-in value and dealer fees — while taxes, title and registration fees set by your state are named as the things you cannot negotiate.

Negative equity is the more serious version. If you still owe $3,000 more on your trade than it is worth and that balance is rolled into the new contract, the payment on the example car goes from $570.27 to $633.24 and the all-in cost from $37,216 to $40,995. The CFPB's guidance on trading in a car that is not paid off puts it plainly: a dealer or lender may offer to roll the balance of your existing auto loan into the new one, but this will make the new loan more expensive. Model it here by adding the shortfall to the price, with one caveat — this calculator will then charge sales tax on it, about $180 at a 6% rate, where a real contract usually would not.

Auto Loan Payment Chart

Everything below is computed by this page's formula on a clean $10,000 financed — no tax, no down payment, no trade — so the figures scale to any loan. Multiply by your amount financed divided by 10,000.

Monthly payment per $10,000 financed

Financing $28,800 at 7% over 60 months? That is 2.88 × $198.01 = $570.27, the same answer the calculator returns, because it is the same arithmetic.

Total interest per $10,000 financed

The payment table hides the cost; this one shows it. Same loans, total finance charge over the full term:

Read down the 60-month column and each additional point of APR costs between $277 and $293 more per $10,000 borrowed. Read across the 7% row and the same $10,000 costs $1,116 over three years or $2,678 over seven — the term more than doubles the price of the money while the monthly figure falls by half.

What a monthly budget actually finances

The same arithmetic inverted, at a 7% APR. If you know what you can pay each month, this is the amount financed that payment supports; add your down payment and take off the sales tax to get back to a car price:

A $500 budget finances $16,193 over three years or $33,128 over seven at the same rate. The second car is not twice as affordable; it is the same $500 collected 28 more times.

How to Read Your Result

The calculator returns four lines, ordered deliberately: the one the dealer wants to discuss first, then the three that decide whether the deal is any good.

The four lines

• The payment — what leaves your account every month for the whole term. Test it against your budget after insurance, fuel and maintenance are already subtracted, not against your gross pay.
• The financed amount, with its build-up — price, plus tax, minus down, minus trade. Check this against the purchase order line by line. If it does not match, something has been added that you did not agree to.
• Total interest — the finance charge, and the honest price of borrowing. This is the number to compare between competing offers, because a lower payment on a longer term always loses on this line.
• All-in cash cost — payments plus your down payment. It excludes the trade-in vehicle, since that was not cash out of your account. Set it against the price of the car and you have the real cost of buying on credit.

If the tool returns a "Check your inputs" notice instead, one of three things happened: the price is blank or zero, the APR falls outside the accepted 0–40% range, or your down payment plus trade-in already covers the price and tax, leaving nothing to finance.

Changing the term: the lever with the biggest lie in it

The same $28,800 financed at 7%, across all five terms on offer:

Going from 60 to 84 months drops the payment by $135.60, a 24% cut, and adds $2,296 to the interest. That trade is sometimes worth making — a payment you can reliably meet beats a payment you default on — but it should be a decision, not a default setting chosen quietly for you.

The deeper cost is equity. This calculator reports totals rather than a month-by-month balance, but the same amortization run forward shows the problem: two years into the 60-month loan the balance stands at $18,469, while the 84-month loan on the identical $28,800 still owes $21,952. That extra $3,482 of debt sits against a car that has been losing value the whole time, and the longer the term, the longer the stretch where the loan exceeds what the vehicle is worth. GAP insurance exists for exactly that window — the CFPB describes it as an optional product intended to cover the difference between what you owe and what the insurer pays if the car is stolen or totaled.

To watch the balance fall payment by payment rather than seeing only the totals, run the same figures through the Loan Repayment Calculator.

Changing the APR: what a credit score is worth in dollars

The same $28,800 over 60 months, moving only the rate:

The spread between a prime 4% and a deep-subprime 20% on the identical car is $232.62 a month and $13,957 in interest — close to half the price of the vehicle, decided by a credit tier rather than by anything about the car. If your quoted rate sits in the lower half of this table, the term is your main lever; if it sits in the upper half, the rate is, and an hour spent on a credit-union pre-qualification is worth more than any amount of haggling over price.

Is the payment affordable?

The most durable rule of thumb in car buying is 20/4/10: at least 20% down, no more than a four-year term, and total vehicle costs — payment, insurance, fuel, maintenance — under 10% of gross income. It comes from consumer-finance advice rather than any regulator, and its value is not the exact numbers but the fact that it pins all three levers at once, so a lower payment cannot be manufactured by quietly stretching one of them.

Applied to the $30,000 car at 7%, that means $6,000 down over 48 months: a payment of $617.81, $3,855 of interest, $35,655 all-in. The opposite deal — nothing down over 84 months — is $479.95 a month, $8,516 of interest, $40,316 all-in. The disciplined version costs $137.86 more each month and $4,661 less overall, and it is the one where you hold equity in the car from the first year rather than the fifth.

The payment has consequences beyond the car, too. Mortgage underwriting counts an auto payment inside your total debt-to-income ratio, so several hundred dollars a month on a vehicle directly reduces the mortgage you qualify for.

If a house purchase is anywhere on the horizon, price that cost before you sign anything, using the Home Affordability Calculator.

Limits: When This Calculator Does Not Apply

This is an amortization model of a clean retail installment contract. Here is what it deliberately does not do, so you know where to stop trusting it:

• It models no fees. Documentation fees, title, registration and destination charges are not separate inputs — add them to the vehicle price if you want them financed, and accept that the model will then apply sales tax to them, which may not match your state's treatment.
• It assumes the first payment falls one month after signing. Dealers frequently arrange a 45- or 60-day first payment, and the extra weeks of accrued interest make the real first payment, or the final payoff, slightly larger than shown.
• It uses monthly amortization. Most US auto loans accrue simple interest daily, so paying a few days early or late shifts the split between interest and principal; the payment does not change, but a payoff quote will differ by a few dollars from the totals here.
• It does not model precomputed-interest contracts, where the finance charge is fixed at signing and paying early saves less than you would expect. If your paperwork says precomputed, ask the lender directly what an early payoff saves.
• The term list stops at 84 months. Contracts of 96 months exist; this calculator cannot model them, and the interest tables above are a fair argument for why that is not much of a loss.
• It assumes a fixed rate for the whole term. Variable-rate auto loans are rare in the US but not extinct, and the payment on one will move.
• Leases are a different instrument entirely — built on residual value and a money factor rather than an amount financed — so none of this transfers to a lease quote.
• The trade-in tax credit is the majority rule, not a universal one. In a state that gives no credit, move the trade-in figure into the Down Payment field as described above.
• It does not know your rate. The APR is whatever you type; there is no rate table behind it, deliberately, because published averages go stale and your real quote depends on your credit tier, the term, and whether the car is new or used.
• It excludes running costs — insurance, fuel, maintenance, tires, registration renewals. Those routinely rival the payment itself, and a car that passes the payment test can still fail the budget.

What the tool is reliable for is the arithmetic of the contract itself: given a price, a tax rate, cash in, a rate and a term, the payment, the finance charge and the all-in cost are exact.