Auto Loan Calculator
Calculate accurate monthly car payments, trade-in equity deductions, state sales tax, and total financing interest with our interactive amortization engine.
Loan Parameters
Configure vehicle pricing and credit terms
Trade-ins reduce your sales tax base in most jurisdictions.
Applied to taxable vehicle price: $35,000
Out-the-Door Loan Accounting
Dynamic Amortization Schedule
Month-by-month and annual breakdown of principal paydown and interest accrual
| Period | Payment | Principal | Interest | Total Interest | Remaining Balance |
|---|---|---|---|---|---|
| Month 1 (Yr 1) | $581.63 | $442.07 | $139.56 | $139.56 | $30,007.93 |
| Month 2 (Yr 1) | $581.63 | $444.09 | $137.54 | $277.10 | $29,563.84 |
| Month 3 (Yr 1) | $581.63 | $446.13 | $135.50 | $412.60 | $29,117.71 |
| Month 4 (Yr 1) | $581.63 | $448.17 | $133.46 | $546.06 | $28,669.53 |
| Month 5 (Yr 1) | $581.63 | $450.23 | $131.40 | $677.46 | $28,219.31 |
| Month 6 (Yr 1) | $581.63 | $452.29 | $129.34 | $806.80 | $27,767.01 |
| Month 7 (Yr 1) | $581.63 | $454.36 | $127.27 | $934.06 | $27,312.65 |
| Month 8 (Yr 1) | $581.63 | $456.45 | $125.18 | $1,059.24 | $26,856.20 |
| Month 9 (Yr 1) | $581.63 | $458.54 | $123.09 | $1,182.34 | $26,397.66 |
| Month 10 (Yr 1) | $581.63 | $460.64 | $120.99 | $1,303.33 | $25,937.02 |
| Month 11 (Yr 1) | $581.63 | $462.75 | $118.88 | $1,422.20 | $25,474.27 |
| Month 12 (Yr 1) | $581.63 | $464.87 | $116.76 | $1,538.96 | $25,009.40 |
How Auto Loan Interest & Vehicle Financing Work
Securing a vehicle loan is one of the largest capital decisions most households make. Understanding how lenders compute your monthly payment, how interest amortizes, and how trade-in allowances affect state sales tax empowers you to save thousands at the dealership.
01. The Closed-Form Amortization Equation
Most auto loans utilize simple interest amortization. Your fixed monthly payment is derived by multiplying your principal balance against the monthly periodic rate (APR ÷ 12) compounded across your contracted loan term. Because early payments carry a larger outstanding balance, the majority of your early payments go toward interest rather than principal paydown.
02. The Hidden Trap of 72 & 84-Month Terms
Dealership finance offices frequently pitch 72- or 84-month terms to make high vehicle prices seem affordable on a monthly basis. However, long loan terms accelerate negative equity (being "underwater"), where your vehicle depreciates faster than you pay off the debt. Sticking to 48 or 60 months ensures you build positive vehicle equity quickly.
03. State Sales Tax & Trade-In Tax Credits
In over 40 states, state lending laws grant a trade-in tax deduction. If you purchase a $40,000 vehicle and trade in your existing car for $15,000, you only pay state sales tax on the remaining $25,000. At an 8% sales tax rate, this trade-in tax credit immediately saves you $1,200 in out-of-pocket tax obligations.
04. Out-the-Door Price vs. Sticker Price
A common car-buying mistake is negotiating strictly around the window sticker price. Your out-the-door price includes mandatory government fees (registration, title, licensing), state sales tax, and dealer documentation fees. Always base your financing calculations on the final out-the-door price to avoid surprise financing charges.
Comparing Personal Loans vs. Auto Loans?
Purchasing an older used car or buying from a private seller? Check out our Personal Loan Calculator to compare unsecured loan APRs and calculate total borrowing fees.
Frequently Asked Questions About Auto Financing
Q: Should I trade in my car or sell it privately?
Selling privately usually nets 10% to 20% more cash than a dealer trade-in offer. However, trading in your vehicle offers unmatched convenience and a significant state sales tax credit in 42+ US states. In these states, sales tax is only levied on the difference between the new car purchase price and your trade-in allowance, which often narrows the financial gap between selling privately and trading in.
Q: What is considered a good auto loan interest rate (APR) in 2026?
For borrowers with excellent credit (FICO scores 720 and above), a competitive auto loan APR typically ranges from 4.9% to 6.5% for new vehicles and 6.0% to 7.9% for certified pre-owned or used vehicles. Borrowers with fair or subprime credit scores (below 660) should expect rates ranging from 9.5% to 18% or higher.
Q: How does loan term length impact my total car financing cost?
While extending your loan term to 72 or 84 months lowers your monthly installment, it substantially increases your total interest charges over time and exposes you to negative equity ("underwater" loan). A 72-month loan at 6% APR can cost nearly double the total interest of a 48-month loan for the exact same vehicle.