$6,344.
That's how much extra you pay on a $28,000 car financed at 7% for 72 months. It doesn't buy you more car. Every dollar goes straight to the lender.
Most buyers never see that number because every dealership conversation runs through monthly payment. At $477 a month, the loan feels fine. The total cost doesn't come up.
This guide breaks down exactly where that $6,344 comes from. You'll see what drives your monthly payment and how to keep thousands more in your pocket before you sign.
TL;DR
- Auto loan interest is front-loaded — you pay the most interest in the early months when your balance is highest, not spread evenly across the loan.
- The PMT formula drives every car payment: your monthly cost depends on three inputs — loan amount, interest rate, and term length.
- The $10,000 Interest Rule — every $10,000 borrowed at 7% for 5 years costs about $1,880 in interest; at 9%, that becomes $2,455.
- The 20/4/10 rule: 20% down, 4-year max term, all car costs under 10% of monthly gross income — the simplest guardrail against overpaying.
- Getting pre-approved at your bank or credit union takes 15 minutes and removes the dealer's biggest information advantage.
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Calculate My Total Interest Cost — FreeHow Auto Loan Interest Is Calculated
Auto loans use simple interest amortization — each month, you pay interest on what you still owe. As the balance drops, the interest charge drops too. As it shrinks, more of your payment goes toward the principal.
Amortization
Every monthly payment splits into two parts: interest on what you still owe, and a reduction of the loan itself. In month 1 of a $28,000 loan at 7%, your $554 payment splits into $163 of interest and $391 of principal.
Monthly interest charge
Your remaining balance multiplied by one-twelfth of your annual rate. A $28,000 balance at 7% per year = $28,000 × 0.5833% = $163 for that month alone.
Formula
Monthly Interest = Remaining Balance × (Annual Rate ÷ 12)
Month 1 — $28,000 balance at 7%: $28,000 × 0.5833% = $163
Month 12 — balance now ~$23,154: $23,154 × 0.5833% = $135
Month 36 — balance now ~$12,381: $12,381 × 0.5833% = $72
Month 60 — balance now ~$551: $551 × 0.5833% = $3
This is why early payments feel like they barely touch the principal. The interest comes out first, every single month — and only what's left reduces your balance.
How Your Monthly Payment Is Calculated
Every car payment — no matter the bank or car — uses the same formula: the PMT formula.
Formula
M = P × [r(1 + r)ⁿ] ÷ [(1 + r)ⁿ − 1]
Where: M = monthly payment P = principal (loan amount after down payment) r = monthly interest rate (annual rate ÷ 12) n = total number of payments (term in months)
Example: $28,000 loan at 7% for 60 months r = 7% ÷ 12 = 0.005833 n = 60 (1.005833)⁶⁰ ≈ 1.4176
M = 28,000 × (0.005833 × 1.4176) ÷ (1.4176 − 1) M = 28,000 × 0.008270 ÷ 0.4176
➜ M ≈ $554/month
Result: $554/month × 60 months = $33,240 total paid. Minus the $28,000 principal = $5,240 in interest.
That $5,240 is what borrowing costs you. It changes a lot based on two things: your loan term and your rate.
Your First Payment vs Your Last
Here's how a $28,000 loan at 7% over 60 months plays out from start to finish:
| Payment | Interest Portion | Principal Portion | Remaining Balance |
|---|---|---|---|
| Month 1 | $163 (29%) | $391 (71%) | $27,609 |
| Month 12 | $135 (24%) | $419 (76%) | $23,154 |
| Month 24 | $105 (19%) | $449 (81%) | $17,959 |
| Month 36 | $72 (13%) | $482 (87%) | $12,381 |
| Month 48 | $37 (7%) | $517 (93%) | $6,417 |
| Month 60 | $3 (1%) | $551 (99%) | $0 |
In month 1, nearly 30 cents of every dollar goes to interest. By month 60, almost nothing does.
This front-loading has a real-world impact. Refinancing in year 1 or 2 saves the most money. Your balance is still high then, so you're cutting out the most expensive months ahead. Wait until year 4 and most of the interest savings are already paid and gone.
How Loan Term Changes Your Total Cost
Same $28,000 car. Same 7% rate. Just different term lengths.
| Term | Monthly Payment | Total Interest | Total Paid |
|---|---|---|---|
| 36 months | $864/mo | $3,104 | $31,104 |
| 48 months | $671/mo | $4,208 | $32,208 |
| 60 months | $554/mo | $5,240 | $33,240 |
| 72 months | $477/mo | $6,344 | $34,344 |
| 84 months | $423/mo | $7,532 | $35,532 |
Going from 60 to 84 months saves $131/month — but adds $2,292 in total interest. You're paying $131 less per month while handing the lender $2,292 over two extra years.
Most buyers miss a second cost. On an 84-month loan, you'll almost certainly owe more than the car is worth for the first three or four years. If you sell or total the car in those early years, you may owe money even after the insurance check.
Shorter terms always cost more per month. They always cost less overall.
How Your Down Payment Changes Everything
A bigger down payment does two things most buyers don't expect. It lowers your monthly payment. And it keeps you from owing more than the car is worth.
| Down Payment | Loan Amount | Monthly Payment | Total Interest |
|---|---|---|---|
| $0 (0%) | $28,000 | $554/mo | $5,240 |
| $2,800 (10%) | $25,200 | $499/mo | $4,740 |
| $5,600 (20%) | $22,400 | $444/mo | $4,240 |
| $8,400 (30%) | $19,600 | $388/mo | $3,280 |
Going from 0% down to 20% down saves $110/month and nearly $1,000 in total interest. But the bigger win is protection.
A new car typically loses 20% of its value in year one. Put nothing down and your loan balance and the car's value are immediately out of sync. With 20% down, you start roughly even — which means you're not trapped if life forces an early sale.
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Run Your Down Payment Comparison — FreeHow Your Interest Rate Changes Total Cost
Hold the term at 60 months and change only the rate. Same $28,000 loan.
| Rate | Monthly Payment | Total Interest |
|---|---|---|
| 5% | $528/mo | $3,680 |
| 7% | $554/mo | $5,240 |
| 9% | $581/mo | $6,860 |
| 12% | $623/mo | $9,380 |
The monthly payment difference between 5% and 12% is just $95. But the total interest difference is $5,700 — over 5 years, on the exact same loan amount.
That $5,700 gap is entirely determined by your credit score. Buyers with 720+ scores typically qualify for 5–7%. Buyers with 620 scores often see 10–13%.
Formula
The $10,000 Interest Rule — total interest per $10,000 borrowed over 5 years:
At 5% → $1,322 in total interest At 7% → $1,880 in total interest At 9% → $2,455 in total interest At 12% → $3,346 in total interest
Scale to your loan amount: $28,000 at 7% for 5 years → 2.8 × $1,880 = ~$5,264 (actual: $5,240) ✓ $35,000 at 9% for 5 years → 3.5 × $2,455 = ~$8,593 $20,000 at 12% for 5 years → 2.0 × $3,346 = ~$6,692
Use this to gut-check any loan quote in seconds.
Your rate is the factor you control most — and the one with the biggest dollar impact over the life of any loan.
Dealer Financing vs Bank Pre-Approval
Dealer financing is not there to get you the best rate. It's a profit center. The dealer places your loan with a lender and earns a fee called "dealer reserve." That fee gets added to the rate you're quoted. You're typically seeing a higher rate than you'd qualify for at your own bank.
Getting pre-approved somewhere else first closes that gap for good.
Formula
Example: $28,000 loan at 60 months
Dealer rate: 9% Monthly payment: $581/mo Total interest: $6,860
Pre-approved bank rate: 6% Monthly payment: $541/mo Total interest: $4,460
Savings from pre-approval: $40/month → $2,400 over 5 years
When you focus only on monthly payment, the dealer controls the math. They can stretch a 48-month loan to 72 months, drop the payment by $150, and collect thousands more in total interest. You walk away feeling like you got a deal. The lender collected $2,000 extra.
Getting pre-approved takes 15 minutes online. Apply at your bank, your credit union, and at least one online lender before you set foot on a lot. If you apply at several lenders within 14 days, it counts as just one credit check. Walk in with a confirmed rate — the dealer either beats it to earn your financing business, or you use your own.
The 20/4/10 Rule: Your Car Budget Framework
Formula
The 20/4/10 Rule: 20% — Put at least 20% down on the car 4 — Finance for no more than 4 years (48 months) 10 — Keep all car costs under 10% of monthly gross income (payment + insurance + estimated maintenance)
Example 1 — $5,000/month gross income: 10% cap = $500/month for all car costs Insurance: $130/mo | Maintenance: $50/mo Max payment: $320/month → loan ≈ $13,100 → max car price ≈ $16,400
Example 2 — $6,000/month gross income: 10% cap = $600/month for all car costs Insurance: $150/mo | Maintenance: $50/mo Max payment: $400/month → loan ≈ $16,400 → max car price ≈ $20,500
Example 3 — $8,000/month gross income: 10% cap = $800/month for all car costs Insurance: $175/mo | Maintenance: $75/mo Max payment: $550/month → loan ≈ $22,500 → max car price ≈ $28,100
This rule is conservative by design. The 10% cap on your payment leaves room for insurance and maintenance. Most new car buyers forget those costs until the first bill shows up.
If the 20/4/10 rule says you can afford a $20,500 car but you're looking at $28,000, a longer loan term won't fix it. It'll just hide it for a few years.
The 2026 Auto Loan Interest Tax Deduction
Starting in 2025, you can deduct up to $10,000 of interest on a qualifying new car loan. You don't need to itemize your taxes to claim it.
Key eligibility requirements:
- The vehicle must be new — used cars and leases do not qualify
- Final assembly must occur in the United States
- The loan must be for personal use (not business or commercial)
- Income limit: the deduction drops by $200 for every $1,000 you earn above $100,000 (single) or $200,000 (joint)
Formula
2026 Auto Loan Interest Deduction — What It's Worth:
Max deduction per return: $10,000 Applies to: new U.S.-assembled vehicles, personal use, loans originated Jan 1, 2025 or later
Tax savings on $28,000 loan at 7% for 60 months ($5,240 total interest): At 22% bracket → ~$1,153 in federal tax savings At 24% bracket → ~$1,258 in federal tax savings At 32% bracket → ~$1,677 in federal tax savings
Your lender sends Form 1098-VLI if you paid $600+ in interest during the year. Claim it on Form 1040, Schedule 1-A.
On the $28,000 loan used in this article, you'd pay $5,240 in total interest. The entire amount qualifies — it's under the $10,000 limit. At the 22% bracket, that's over $1,100 back at tax time. Over five years, that's about $230 back per year. It won't change which car you pick, but it can tip the balance when you're choosing between two loan deals.
This deduction also covers loans you took out in 2025. If you financed a new qualifying vehicle last year, you can claim the interest paid on your 2025 return.
The deduction doesn't change how interest builds up. You still pay more interest in the early months. But it does lower the true cost of the loan. It's also one more reason to check if the car you want was built in the U.S. before you sign.
When an Auto Loan Works Against You
The same formula that sets your payment also controls how fast your loan balance falls behind what the car is worth.
Negative equity
When you owe more on the loan than the car is worth. For example: you owe $22,100 on a car now worth $20,200 — you're $1,900 in the hole if you need to sell or trade in.
A new $28,000 car loses roughly 20% in year one and about 10% per year after that. Here's where you stand at the end of year 2 on a 72-month loan with no down payment:
| Value | |
|---|---|
| Car value after 2 years | ~$20,200 |
| Loan balance remaining | ~$22,100 |
| Gap (negative equity) | −$1,900 |
You owe $1,900 more than the car is worth. If you total the car or need to sell, you're writing a check on top of whatever the insurance pays. This isn't the worst case. It's how most 72- and 84-month loans play out when you put little or nothing down.
5 Steps to Keep Your Total Interest Down
1. Get pre-approved before you visit a dealership
Apply at your bank, your credit union, and one online lender. If you apply at several lenders within 14 days, it counts as just one credit check. Walk in with a rate the dealer has to beat.
2. Use the 20/4/10 rule to set your ceiling
Take 10% of your gross monthly income. Subtract insurance ($120–200/mo) and maintenance ($50–100). What's left is your maximum monthly payment. Use the auto loan calculator to find the loan amount that hits that number — then add 20% down to get your real max car price.
3. Finance for the shortest term your budget can support
Run your loan amount at 48 months and 60 months side by side. If the difference is $80–100/month, the shorter term is almost always worth it. If it's $200/month, that's a signal the car may be too expensive — not that the loan term should get longer.
4. Put at least 20% down to shrink your interest-bearing balance
Every dollar you put down is a dollar you don't pay 7–12% interest on for the next 4–6 years. It also keeps you from owing more than the car is worth in those first few years when the car loses value fastest.
5. Refinance early if your credit score has improved
Because you pay the most interest early, refinancing in the first 18–24 months saves the most. Your balance is still high then, and the costly months are still ahead. Even a 2-point rate drop on a $22,000 balance saves roughly $1,200 over the remaining term.
What This Means for Your Car Budget
The monthly payment is a cash-flow number. The total interest is the actual cost of financing the car.
On a $28,000 car at 7% for 60 months, you pay $5,240 in interest — 19% of the sticker price just for borrowing. Stretch that to 84 months at 9% with no down payment and the interest exceeds $10,400. That's over a year's worth of payments for nothing but lender profit.
Know your total cost before you agree to a monthly payment. Get pre-approved. Run the 20/4/10 check. Compare term scenarios. When you walk in with those numbers, you're buying a car — not being sold one.
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See My Total Auto Loan Cost — FreeCommon Questions
Sources & Methodology
Payment calculations use the standard PMT amortization formula: M = P × [r(1 + r)ⁿ] ÷ [(1 + r)ⁿ − 1], where P is the loan principal, r is the monthly interest rate (annual rate ÷ 12), and n is the number of monthly payments. Total interest figures are calculated as (monthly payment × number of payments) − principal. Amortization schedule figures use iterative balance reduction: each month's interest = remaining balance × monthly rate; principal = monthly payment − interest. Depreciation estimates are based on typical industry averages; actual depreciation varies by make, model, condition, and mileage. Rate benchmarks are illustrative based on general market conditions; actual rates vary by lender, borrower credit profile, and vehicle type.
Sources: Consumer Financial Protection Bureau — Auto Loans, Federal Reserve — Consumer Credit G.19 Statistical Release, Bankrate — Auto Loan Rates, May 2026, IRS — Treasury and IRS Guidance on the Auto Loan Interest Deduction.
Disclaimer: Results are for educational and informational purposes only. FiscalCalc is not a licensed financial advisor, mortgage broker, or tax professional. Consult a qualified professional before making major financial decisions.