Auto Loan Hidden Cost Revealer
By vehicle model
Auto Loan Cost Calculator — Interest vs Car Price
What this calculator does
Enter the car price, down payment, loan term, and APR. This calculator shows the monthly payment, total interest, and a breakdown of car cost versus interest.
The math, with a worked example
Loan amount = price − down payment. Monthly payment = P × (r(1+r)^n) ÷ ((1+r)^n − 1), where r is monthly rate and n is term. Total interest = payment × n − loan amount. A $30,000 car with $5,000 down, 72 months, and 7.5% APR has a monthly payment of $432.25 and total interest of $6,122, or $36,122 paid out once the down payment is counted.
Why this matters
Stretching a car loan shrinks the payment and grows the price: $432 a month for 72 months feels manageable while quietly adding $6,122 of interest to a $30,000 car. The payment is what you feel; the total interest line is what you pay.
Methodology and transparency
Monthly payment uses the standard amortization formula P × (r(1+r)^n) ÷ ((1+r)^n − 1); total interest = payment × n − principal. The formula is exact for a fixed-rate simple-interest loan — the real-world gaps are add-ons financed into the principal (warranties, GAP, fees) and the negative-equity risk of long terms: 72+ months underwater on a depreciating asset means owing more than the car's worth for most of the loan. Everything runs in your browser; no data is sent or stored.
Last reviewed: 2026-08-08
Common questions
How does a longer term affect total cost?
Longer terms lower the monthly payment but increase total interest. You also risk owing more than the car is worth.
What is negative equity?
When you owe more on the loan than the car is worth. This happens easily with long-term loans and low down payments.
Should I put more down?
A larger down payment reduces monthly payments, total interest, and negative-equity risk.