Work out the real interest rate on a fixed-term loan when a dealer or lender only gives you the monthly payment and total price — not the rate itself.
Some lenders and dealers structure an offer entirely around the monthly payment and total price, without stating the interest rate directly — sometimes just for simplicity, sometimes because a payment-focused pitch is easier to sell than a rate-focused one. Either way, the rate is fully determined by the loan amount, term, and payment; it's just a matter of solving for it instead of being told it outright.
A monthly payment alone can't tell you whether a deal is good — a lower payment stretched over a longer term can hide a worse rate. Working out the actual rate lets you compare two offers on equal footing, the same way APR lets you compare loans with different fee structures.
Then there's no finite positive interest rate that fits — the payment has to be large enough to eventually retire the full loan amount within the given term for a rate to exist.
Yes, as long as it's a standard fixed-rate, fixed-term loan with equal monthly payments — auto loans, personal loans, and most installment loans all fit this pattern.
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