Auto Loan Early Payoff Calculator

What this computes

"Should I pay extra on the car?" usually gets answered with a vague "it helps." This puts a number on it. It derives your scheduled payment from the current balance, APR, and months left, then simulates the loan twice — exactly as scheduled, and with your extra payment and/or lump sum — and reports the interest saved and the time cut.

The math

Interest each month is balance × (APR / 12). The payment covers that interest first; the rest reduces principal. Any extra is pure principal reduction:

interest_m   = balance × (APR / 12)
principal_m  = payment − interest_m + extra
balance     -= principal_m   (until it hits zero)

Because every future month's interest is charged on that now- lower balance, the saving compounds over the whole remaining term. A lump sum applied today gets the maximum number of months of that compounding.

A dollar of extra principal stops earning the lender interest for every month left on the loan. That's why early dollars matter most.

How to use this

1. Use today's real balance, not the original loan amount — early payoff math runs from where you are now.
2. Test a sustainable monthly extra before a heroic one. A modest amount you actually keep paying beats a large one you abandon.
3. Compare lump sum vs keeping cash. If your APR is high, principal reduction is a guaranteed return; weigh it against your emergency fund.
4. Tell the lender "apply to principal." Otherwise extra may just advance your due date and save nothing.

When NOT to pay it off early

• No emergency fund yet. Cash sunk into a car loan is hard to get back. Liquidity first.
• Higher-rate debt exists. Credit-card balances almost always cost more than an auto loan — pay those first.
• A 0% or very low promotional APR. There's little or no interest to save; the money works harder elsewhere.
• Precomputed-interest loan. Savings are reduced; confirm the loan is simple-interest before committing.

What this calculator doesn't model

• Precomputed interest / Rule of 78s. Assumes a simple-interest loan, the common case.
• Prepayment penalties. Rare on auto loans but check your contract.
• Opportunity cost. It doesn't compare the guaranteed interest saving to investing the same cash — see True Cost of Ownership for the broader picture.