Why the payment is not just principal ÷ number of months#
A fixed-rate loan is not simply divided evenly across its term — each payment is a mix of interest (calculated on the remaining balance) and principal, and the mix shifts over time as the balance shrinks. Early payments are mostly interest; later ones are mostly principal. This tool uses the standard amortization formula — the same one lenders use to compute a fixed monthly payment that stays level for the entire term while correctly accounting for compounding interest on the declining balance.
Why the term in years matters more than it looks like it should#
A shorter term produces a noticeably higher monthly payment but a dramatically lower total interest cost — spreading the same loan over 15 years instead of 30 roughly doubles the monthly payment but can cut total interest paid by more than half, because less time means less opportunity for interest to accrue on the outstanding balance. This tool shows total interest specifically so that trade-off is visible, not just the monthly number most calculators lead with.
What this does not include#
This calculates the core loan payment from principal, rate and term only — it does not include property taxes, insurance, PMI, or other costs sometimes bundled into a real-world mortgage payment. For a loan with those additional costs, the number here is the loan payment itself, not the full amount that might appear on an actual bill.