The payment is not all principal
At the start of a fixed-rate loan, a larger share of each payment usually goes to interest because the outstanding balance is still high. As the balance falls, the interest part gets smaller and more of the same payment reduces principal.
The formula
Payment = P x r(1 + r)^n / ((1 + r)^n - 1)
P is the amount financed, r is the periodic interest rate and n is the number of payments. For monthly payments, divide the annual rate by 12 and multiply years by 12.
What changes total cost most
- Interest rate: a small rate difference can add up over a long term.
- Term length: a longer term usually lowers the monthly payment but increases total interest.
- Fees: upfront fees may not change the scheduled payment unless financed, but they still affect the real cost.
- Extra principal payments: paying extra can reduce both payoff time and interest, if the lender applies the extra amount to principal.
How to compare loan offers
Compare monthly payment, total interest, total cost including fees and whether prepayment penalties apply. A lower monthly payment is not automatically cheaper if the term is longer or fees are higher.
Use the calculator
First-payment amortization example
For a 250,000 loan at 6% annual interest over 30 years, the monthly rate is 0.5% and the fixed principal-and-interest payment is about 1,499. In the first month, interest is about 1,250 because 250,000 x 0.005 = 1,250. Only about 249 goes to principal.
Later in the schedule, the interest part falls because the remaining balance is lower. This is why the same monthly payment can be mostly interest early and mostly principal late in the loan term. Extra payments reduce future interest only when they are applied to principal.
FAQ
Why is early interest so high?
Interest is based on the remaining balance. Early in the loan, the balance is high, so more of each fixed payment goes to interest.
Does a lower monthly payment mean a cheaper loan?
Not always. A longer term can lower the monthly payment while increasing total interest. Compare total cost, not only monthly payment.
Do extra payments always save interest?
They usually can when applied to principal, but lender rules, prepayment penalties and payment processing policies matter.
References
- Consumer Financial Protection Bureau: auto loans, accessed 2026-05-16.
- Consumer Financial Protection Bureau: loan amortization schedule, accessed 2026-05-16.
Last reviewed: 2026-05-16.