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Negative Equity Car Calculator

Compare value against payoff and roll a shortfall into a new loan with AI-powered step-by-step solutions
Equity on a car worth $14,500 with an $18,200 loan payoff
Amount financed on a $32,000 car with $3,700 of negative equity rolled in
Monthly payment on $35,620 at 7% over 72 months
When does a $35,620 loan at 7% fall below a car depreciating 15% a year?

Equity Is One Subtraction

Equity in a vehicle is its market value minus what you still owe:

E=V−BE = V - B

  • VV — market value, whatever a buyer or dealer will actually pay today
  • BB — the payoff: the outstanding balance plus interest accrued since the last payment, which is slightly more than the balance shown on a statement

E>0E > 0 is positive equity; E<0E < 0 is negative equity, also called being upside down or underwater. There is no formula for VV — it comes from a valuation guide or an offer. The math starts once you have it.

Negative equity appears because the two curves move differently. A loan balance falls slowly at first, since early payments are mostly interest:

Bk=P(1+r)k−M⋅(1+r)k−1rB_k = P(1+r)^k - M\cdot\frac{(1+r)^k - 1}{r}

while value falls fast and early, roughly geometrically:

Vk=V0(1−d)k/12V_k = V_0 (1-d)^{k/12}

with dd the annual depreciation rate. A small down payment, a long term and a high rate all push the crossover later.

Rolling a Shortfall Into the Next Loan

When a car with negative equity is traded, the shortfall does not disappear — it is added to the new loan:

A=Price+Tax and fees−Down−Trade-in allowance+Old payoffA = \text{Price} + \text{Tax and fees} - \text{Down} - \text{Trade-in allowance} + \text{Old payoff}

The last two terms are the whole story. If the allowance exceeds the payoff you subtract net equity; if the payoff exceeds the allowance you add the difference, and now you are financing part of a car you no longer own.

The payment on the result is the ordinary amortised-loan formula:

M=A⋅r(1+r)n(1+r)n−1,r=APR12M = A\cdot\frac{r(1+r)^n}{(1+r)^n - 1}, \qquad r = \frac{\text{APR}}{12}

and the total interest is nM−AnM - A.

Two things worth computing before signing

  1. The starting equity of the new deal: new car value−A\text{new car value} - A. Rolling a shortfall in guarantees this starts negative.
  2. The break-even month: the first kk where Vk≥BkV_k \ge B_k.

Whether sales tax applies to the full price or to the price net of the trade-in is a jurisdictional rule, and it changes AA. Use the rule that applies where you are.

Common Mistakes to Avoid

  • Using the statement balance as the payoff: the payoff includes interest accrued since the last payment. It is always a little higher.
  • Confusing the trade-in allowance with the car's value: a generous-looking allowance paired with a higher price is arithmetic sleight of hand. Compare AA across offers, never the allowance alone.
  • Believing a longer term makes the shortfall smaller: stretching to 84 months lowers MM but raises nM−AnM - A and delays the break-even month, which is what created the negative equity in the first place.
  • Netting equity the wrong way round: negative equity is added to the amount financed, not subtracted.
  • Assuming straight-line depreciation: value drops fastest in the first year. A linear estimate makes the underwater period look shorter than it is.
  • Forgetting gap coverage exists as a separate question: if the car is written off while B>VB > V, the shortfall is still owed. That is an insurance matter, not a calculation.

Examples

Step 1: E=V−B=14,500−18,200E = V - B = 14{,}500 - 18{,}200
Step 2: = -\3{,}700$
Step 3: The shortfall is 3,700/18,200≈20.3%3{,}700/18{,}200 \approx 20.3\% of the outstanding balance
Answer: -\3{,}700—negativeequityof— negative equity of$3{,}700$

Step 1: Tax: 32{,}000 \times 0.06 = \1{,}920$
Step 2: A=32,000+1,920−2,000−14,500+18,200A = 32{,}000 + 1{,}920 - 2{,}000 - 14{,}500 + 18{,}200
Step 3: = 33{,}920 - 2{,}000 - 14{,}500 + 18{,}200 = \35{,}620$
Step 4: At 7% APR over 72 months: r=0.07/12≈0.0058333r = 0.07/12 \approx 0.0058333, (1+r)72≈1.5201(1+r)^{72} \approx 1.5201
Step 5: M = 35{,}620 \times \dfrac{0.0058333 \times 1.5201}{0.5201} \approx \607.29$
Step 6: Total interest: 72 \times 607.29 - 35{,}620 \approx \8{,}104.56$
Step 7: Starting equity on the new car: 32{,}000 - 35{,}620 = -\3{,}620$
Answer: \35{,}620financed,aboutfinanced, about$607.29amonth,a month,$8{,}104.56ofinterest—andthenewdealstartsof interest — and the new deal starts$3{,}620$ underwater

Step 1: Balance: Bk=35,620(1.0058333)k−607.29(1.0058333)k−10.0058333B_k = 35{,}620(1.0058333)^k - 607.29\dfrac{(1.0058333)^k - 1}{0.0058333}
Step 2: Value: Vk=32,000×0.85k/12V_k = 32{,}000 \times 0.85^{k/12}
Step 3: Month 12: B \approx \30{,}669vsvsV = $27{,}200—underwaterby— underwater by$3{,}469$
Step 4: Month 24: B \approx \25{,}360vsvsV = $23{,}120—underwaterby— underwater by$2{,}240$
Step 5: Month 36: B \approx \19{,}668vsvsV \approx $19{,}652—shortbyonly— short by only$16$
Step 6: Month 37: B \approx \19{,}175vsvsV \approx $19{,}388—positivebyabout— positive by about$212$
Answer: Break-even in month 37 — a little over three years of a six-year loan spent underwater

Frequently Asked Questions

It means the loan payoff exceeds what the vehicle is worth: E = V − B is negative. Selling or trading the car at its market value would not clear the loan, so the difference has to be paid in cash or rolled into new financing.

Amount financed = price + tax and fees − down payment − trade allowance + old payoff. When the payoff is larger than the allowance, the difference increases the new loan, so you finance part of a car you no longer have.

Value falls fastest in the first year or two while a long amortisation repays principal slowly — early payments are mostly interest. The two curves therefore cross much later. A larger down payment or a shorter term brings the crossover forward.

Ask the lender for a payoff quote good through a specific date. It equals the balance plus per-diem interest from the last payment, and possibly a small fee. Amortisation math reproduces it closely, but the lender's quote is the figure that settles the loan.

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