How to use this planner
Enter your loan amount, interest rate, term in months, and any extra monthly payment you're considering. The planner amortizes the loan month by month and shows the payoff time, total interest, and how many months the extra payment shaves off. The "Extra Monthly Payment" input is the lever to experiment with — try $25, $50, or $100 increments to see how each amount shortens the loan and cuts interest.
What your result means
The summary shows four numbers: monthly payment (principal plus interest), payoff time, interest saved by the extra payment, and months removed from the term. Early in the schedule most of each payment goes to interest, so extra payments applied early in the loan save far more than the same extra payment made later — they reduce principal before more interest accrues on it. If "Interest Saved" looks small, your rate is low or you're already near the end of the term, which limits the impact of prepayment.
When to trust it
The math is exact for a fixed-rate amortizing loan with the inputs you provide. It does not account for variable rates, prepayment penalties (rare on auto loans but worth checking in your contract), or the opportunity cost of putting that cash toward higher-rate debt or investments. If your auto loan rate is below roughly 5%, compare the interest saved here against expected investment returns before committing extra cash. Confirm your actual loan terms with your lender before acting.
Frequently Asked Questions
Is it worth paying off my auto loan early?
It depends on your rate and alternatives. Auto loans above ~7% are usually worth accelerating — the guaranteed interest savings beat expected investment returns. Below ~5%, extra payments are a mediocre use of cash compared with an emergency fund, retirement match, or higher-rate debt. Also check for prepayment penalties first (rare on auto loans, but read the contract).
Should I make extra payments or refinance instead?
They solve different problems. Extra payments attack the balance without changing your terms — best when you have occasional lump sums or a small monthly surplus. Refinancing replaces the loan — best when rates have dropped meaningfully since you signed or your credit has improved, especially early in a long term. If you're near the end of the loan, neither lever moves much: most remaining payments are principal already.
When in the loan term do extra payments help most?
Early. Auto loans amortize front-loaded with interest, so an extra $500 in year one can erase more interest than the same $500 in year four. If your loan is over half paid, run the numbers in the planner before committing — the interest saved may be small enough that the cash is better used elsewhere.