See whether paying cash or financing (and investing the difference) actually costs less for your specific numbers.
This calculator compares two paths to the same car. In the "Pay Cash" path, you hand over the full price and pay zero interest, but that money stops earning anything for you. In the "Finance + Invest" path, you make a down payment (if any), finance the rest at your loan rate, and — critically — the calculator assumes the amount you didn't pay upfront stays invested at your expected return for the full loan term. The net cost of financing is the interest you pay minus whatever that invested cash grew by. If the growth outweighs the interest, financing shows as the winner. If the interest outweighs the growth, cash wins.
Example 1 — average credit, no promo: $30,000 car, no down payment, 6.4% APR over 60 months, and a 4.0% APY savings account for the unspent cash. Monthly payment is about $586, total interest is about $5,135. The $30,000 left invested grows by about $6,630 over the same five years. Net result: financing and investing comes out about $1,495 ahead — but only if that $30,000 genuinely stays untouched for five years.
Example 2 — near-prime credit, no promo: Same $30,000 car, same 4.0% APY, but a 12% APR (typical for near-prime/subprime tiers). Total interest jumps to about $10,040, while the investment growth stays the same at $6,630. Net result: paying cash wins by about $3,410. The higher your loan rate, the more the math tips toward cash — which is why checking your actual rate tier before running this calculator matters.
Cash tends to win when your loan APR is above roughly 7-8% — a common range for near-prime or subprime credit tiers. It also wins by default if you set the expected investment return low (or to 0%), which is the honest number to use if you know the cash would otherwise sit in a low-interest checking account rather than a high-yield account or investment. See our current auto loan rates by credit tier to find your realistic APR before running this calculator.
Financing tends to win when you qualify for a low APR (0-4%, often from manufacturer promotions) and you have a genuine high-yield place to keep the unspent cash — a savings account paying 4%+ APY, a CD, or an existing investment account you won't touch. The wider the gap between your investment return and your loan APR, the more financing pulls ahead. This only holds if you actually leave the money invested; if there's a real chance you'd spend it instead, use a lower expected return to reflect that.
The single biggest way people misuse this kind of comparison is entering an optimistic investment return and then not actually investing the money. If the "unspent" cash ends up in a regular checking account earning 0.4%, or gets spent on something else within the first year or two, the financing route's advantage disappears and cash would have been the better call. Be honest about your own behavior: if you know you'd rather not manage a separate investment account for five years, set the expected return closer to what a plain savings account pays, or just favor cash. The calculator only tells you which choice is better if you follow through — it can't enforce the discipline for you.
It doesn't factor in taxes on investment gains (interest and dividends are usually taxable, which reduces the real-world advantage of the "invest" side), manufacturer rebates that are sometimes only available if you decline 0% financing, or the risk that market/savings returns don't hold steady for the full loan term. It also assumes you make every loan payment on time — missed payments and fees aren't modeled. Treat the result as a starting comparison, not a guarantee, and re-run it with a conservative return estimate if you're unsure you'd stay disciplined about keeping the cash invested.