Start with the question you actually have
Suppose your mortgage payment and car payment are both current, and you can set aside another $200 a month. Should that money go to the car loan or the mortgage? There is no useful answer in the fact that one loan is secured by a house and the other by a car. The decision depends on the rate charged on each balance, the type of car loan, the years or months left, payment rules, fees, and your cash reserve.
This is a question about allocating extra principal payments on loans you already have. If you are preparing to apply for a mortgage and wondering whether to clear the car loan first, see our separate homebuying and debt guide. A new mortgage application introduces debt-to-income and cash-to-close considerations that are different from maintaining two existing loans.
Compare one extra dollar at the same time
On a simple-interest car loan and a standard fixed-rate mortgage, reducing principal means less interest is charged on that principal later. A quick first-month comparison is extra principal x annual interest rate / 12. Put $200 toward a car loan at 8%, and the following month's interest is roughly $1.33 lower than it otherwise would have been. The same $200 toward a mortgage at 5.5% changes the following month's interest by roughly $0.92. These are illustrations under monthly accrual, not lender quotes; a daily-interest car loan depends on posting dates.
The difference grows only while those dollars would otherwise remain borrowed. If the car loan is nearly finished, it may have little future interest left to save. If you expect to sell or refinance the home next year, a mortgage calculator's projected savings through a 25-year payoff can also overstate the benefit you personally keep. Compare the same realistic period and the same amount of extra cash, then check each loan's payoff terms.
Run the auto loan payoff calculator and the mortgage extra payment calculator with your current statements. The two tools use simplified monthly models. Compare their change in interest and payoff time, not their raw total interest: a large mortgage naturally has a much larger lifetime dollar amount.
What a faster car payoff changes
A paid-off car removes a required monthly loan payment. That can matter more than a small difference in modeled interest if the household budget is tight. Paying an extra $200 each month on a $425 car payment might close the loan months sooner; the actual number depends on the remaining balance and rate. Once the balance reaches zero, the entire required payment disappears. Until then, a partial extra principal payment usually does not lower the contractual monthly payment, so keep the required amount in your budget.
Check the contract before treating estimated savings as real. The Consumer Financial Protection Bureau (CFPB) says auto loan prepayment penalties depend on the contract and state law. Its payment allocation guidance explains that due fees and interest generally come before principal. The separate prepayment penalty checklist walks through the exact documents and lender questions.
Also establish whether the car loan uses simple or precomputed interest. CFPB says precomputed interest responds differently to extra payments; an online amortization estimate may not reflect your contract's rebate rules. Ask the lender for an itemized payoff quote if the terms are unclear.
What a faster mortgage payoff changes
Extra mortgage principal usually shortens the remaining term. It generally does not lower next month's required principal-and-interest payment. A recast, where offered, is a separate lender process and may have its own rules and cost. A mortgage payoff calculation can show large lifetime interest savings, but that number assumes you retain the loan and keep up the extra payments long enough to realize them.
Mortgage principal is also less accessible than money in a checking account. A roof repair or job loss can arrive long before the expected payoff date. The CFPB notes that mortgage servicers may allow extra principal payments and advises borrowers to confirm how those payments are applied. Check your statement after the first one. Our mortgage prepayment guide covers liquidity, servicer posting and limits in more detail.
Do not assume the mortgage interest tax deduction cancels the cost of interest. Whether mortgage interest is deductible depends on eligibility and itemizing. The IRS Publication 936 explains the rules; this article does not calculate an after-tax payoff benefit. If the deduction affects your situation, compare after-tax costs rather than the two headline rates alone.
Use a worksheet before moving the money
Take the latest statement for each loan and write down six things: current principal balance, contract interest rate, required payment, months remaining, the exact way extra principal posts, and any charge for the payment you plan to make. For the car loan, note whether interest is simple or precomputed and get a dated payoff quote if you intend to close it. For the mortgage, separate principal and interest from escrow, taxes and insurance. Do not put the full escrow-inclusive payment into a principal-and-interest comparison.
- Choose one equal extra amount. For example, test $200 a month on either loan. Do not compare $200 on one with a $5,000 lump sum on the other.
- Use the same time horizon. If you expect to refinance or move within 3 years, ask each servicer for a schedule or use a tool that shows balances and interest at that point. Our two payoff calculators show lifetime estimates, not a 3-year snapshot.
- Subtract confirmed charges. A fee may erase part of the benefit. Do not invent a penalty because a search result says one is possible; use the contract or lender quote.
- Check the cash left over. Keep enough for the next likely car repair, home expense, insurance deductible or income interruption. Paying down either secured loan is harder to reverse than leaving cash in savings.
- Review higher-cost debt. If a credit card carries a much higher rate, it deserves a separate comparison before either extra car or mortgage payment. Our debt payoff calculator can help run that case.
Two different outcomes from the same $200
In one household, the car loan might carry 9%, the mortgage 5%, and the car has only 18 months left. Paying extra on the car could remove a required payment sooner and simplify the monthly budget. The interest advantage may still be modest because the remaining term is short, so the borrower should inspect actual projected dollars rather than deciding from rates alone.
In another household, the car loan might be at 3%, the mortgage at 7%, and both have years left. Extra mortgage principal may avoid more interest per dollar during the period both balances remain outstanding. But if that family has no emergency savings, directing all spare cash to either loan could be a fragile plan. These rates and terms are hypothetical examples, not current market averages or personalized recommendations.
The middle answer is often practical: keep a cash buffer and use an amount you can sustain. You can change where future extra payments go as a car loan ends, a mortgage rate changes, or household needs change. Document the assumptions used for each comparison so a new statement does not make an old calculation look more precise than it was.
Sources and methodology
- CFPB: auto loan prepayment penalties and state law
- CFPB: auto loan payment allocation
- CFPB: simple versus precomputed car loan interest
- CFPB: mortgage servicer and extra principal payments
- IRS Publication 936: mortgage interest deduction
WealthScope Hub maintains this guide and its linked calculators. The first-month example uses extra principal x annual rate / 12; it does not model daily posting, tax effects, a rate reset, or a lender's contract-specific payoff. Send corrections to wangsuperyu@outlook.com. We do not claim individual professional credentials or independent expert review. Read our editorial policy.
This is educational material, not personalized financial, lending, tax or legal advice. Check your own loan documents and servicer records before making an extra payment. See our disclaimer.