Math the payment before you decide.

How the math works

Personal loans, auto loans and mortgages use the same standard amortization formula. The monthly payment P equals the loan amount L, multiplied by the monthly rate r = APR / 12, divided by 1 minus (1 + r) raised to the negative power of n (the number of months). In plain English: the lender front-loads the interest, so early payments are mostly interest and later payments are mostly principal.

Why the same APR can mean different totals

Term length is the lever most borrowers underestimate. A $20,000 loan at 10% APR over 36 months costs about $3,231 in total interest. Stretch it to 60 months for a lower payment and the interest jumps to $5,496. The monthly payment is friendlier; the total is meaningfully worse. Use the term slider above to see the trade-off in real time.

What's not in this calculator

Origination fees aren't included. Some lenders charge 1–8% off the top, which raises your effective APR. If a lender quotes you 9.99% APR with a 5% origination fee, the true cost is closer to 12% APR. Our guide on what actually moves your APR walks through the numbers.