How to calculate a car loan payment

Car loans add one wrinkle to the mortgage pattern: the down payment. RPN lets you subtract it on the way into PV, without writing anything down.

Problem

A car costs $32,000. You put $5,000 down and finance the rest over 5 years at 7.9%. What is the monthly payment?

Keystrokes

fFINx≷y
0.00
Start clean.
32000ENTER5000−
27,000.00
Price minus down payment: the amount you finance.
PV
27,000.00
Stores the financed amount as the present value.
5g12×n
60.00
60 monthly payments.
7.9g12÷i
0.66
The monthly rate.
PMT
−546.17
Solves for the payment.

Answer

You finance $27,000.00, and the payment is $546.17 a month.

Why it works

ENTER separates the price from the down payment, and − subtracts them. The result is still in the display, so PV stores it directly. This is RPN’s strength: intermediate results flow straight into the next step.

Comparing two offers

To compare a dealer’s 0.9% financing with a cash rebate, change only what differs. Key the new rate with g12÷i or the new amount with PV, then press PMT again. The other registers keep their values.

Questions

What if there’s a trade-in too?

Subtract it as well: 32000 ENTER 5000 − 8000 − PV.