Car Loan Calculator Guide: US Auto Loans + UK HP/PCP

How a Car Loan Calculator Works

Car loans use the same amortization formula as mortgages: M = P × [r(1+r)^n] / [(1+r)^n − 1]. The only differences are the term length and typical rate.

Example: $30,000 loan, 7% APR, 60 months. M = 30000 × (0.00583 × 1.00583^60) / (1.00583^60 − 1) = $594/month. Total paid = $35,640. Total interest = $5,640.

US Auto Loan Terms in 2026

Most US auto loans run 36, 48, 60, 72, or 84 months. Longer terms lower the monthly payment but massively increase total interest.

Same $30,000 at 7%, different terms:

• 36 months: $927/month, $3,372 total interest
• 48 months: $718/month, $4,464 total interest
• 60 months: $594/month, $5,640 total interest
• 72 months: $511/month, $6,828 total interest
• 84 months: $453/month, $8,028 total interest

A 72-month loan costs 2× the total interest of a 36-month loan at the same rate. Worse: the car depreciates faster than you pay down principal, so you often end up "underwater" (owing more than the car is worth) for 2–3 years.

UK Car Finance: HP vs PCP

UK buyers rarely use traditional amortising loans. The two dominant products are:

Hire Purchase (HP): You borrow the full price minus deposit, repay in fixed monthly payments, and own the car at the end. This works like a US amortising loan.

Personal Contract Purchase (PCP): You pay a deposit, then monthly payments that cover only depreciation (not the full value). At the end, you choose: hand the car back, pay a large "balloon payment" to own it, or trade in for a new PCP deal. PCP monthly payments are 30–40% lower than HP but you don't own anything at the end.

2026 UK APRs: HP typically 8–12%, PCP typically 6–10% for prime borrowers. Non-prime rates can exceed 20%.

The Total Interest Trap

Car ads focus on monthly payment, not total cost. Compare these two offers on the same $30,000 car:

• Offer A: $525/month, 72 months → Total paid $37,800
• Offer B: $592/month, 60 months → Total paid $35,520

Offer B costs $67/month more but saves $2,280 over the life of the loan. Always calculate total cost, not just monthly payment, before signing.

New Car vs Used Car Loan Rates

Used car rates are consistently 1–3 percentage points higher than new car rates — lenders view used cars as riskier collateral because value is less predictable. In 2026:

• US new car APR (prime credit): 6–7%
• US used car APR (prime credit): 8–10%
• UK new car PCP: 6–8%
• UK used car HP: 10–14%

How Your Credit Score Changes the Rate

A 100-point FICO difference can swing your car loan APR by 4–6 percentage points. On a $30,000, 60-month loan:

• FICO 780 (superprime): 5.5% APR → $573/month
• FICO 680 (prime): 8.5% APR → $616/month
• FICO 600 (subprime): 14% APR → $698/month

The subprime borrower pays $7,500 more in total interest than the superprime borrower — for the same car. If you can wait 6 months to raise your credit score by 50+ points before buying, the savings almost always exceed inflation on the car's price.

The Down Payment Math

Standard US advice: 20% down on a new car, 10% on a used car. On a $30,000 new car, that is $6,000 down. Benefits:

• Lower loan amount = lower monthly payment
• Lower interest rate (lenders reward lower LTV)
• Less likely to go underwater on the loan
• Lower total interest over the loan's life

UK PCP deals often allow zero deposit but carry a higher APR. If you can put down 10–20%, your APR typically drops 1–2 percentage points.

How to Cut Your Car Loan Cost

1. Get pre-approved from a bank or credit union before visiting the dealer. Their rate becomes the ceiling; dealer financing must beat it to win your business.
2. Choose the shortest term you can afford. Every year added to the loan costs roughly 1.5× the monthly saving in total interest.
3. Put 15–20% down. Lowers the rate and prevents going underwater.
4. Avoid add-ons. Extended warranties, gap insurance, and paint protection add $2,000–5,000 to the loan and carry the loan's interest rate.
5. Make extra payments. Even one extra payment per year knocks months off a 60-month loan.

The Bottom Line

A car loan is the largest single expense most households have outside of housing. Small changes — 1 percentage point lower APR, 12 months shorter term, $3,000 extra down — compound into thousands of dollars saved. Never accept the first offer, and never decide on monthly payment alone.