Read the payment, balance and cost together
A lower periodic payment can reflect a longer term or a larger final balance. Compare the full schedule and upfront fees as well as the first payment. The loan amount here is the amount already borrowed after any down payment; the main calculator’s down-payment field is context only.
Fixed-rate amortization
For principal P, periodic rate r and n payments, the regular payment is P × r / [1 − (1+r)⁻ⁿ]. At zero interest it is P/n. Each row charges interest on the previous balance and applies the remaining scheduled payment plus extra payment to principal. The final payment is capped at the balance plus interest.
We divide the nominal annual rate by 12, 26 or 52. Weekly and biweekly terms are rounded to a whole number of periods. This is not a daily-accrual or accelerated half-monthly-payment model. Calculations retain fractional cents until display, so a lender’s cent-rounded schedule can differ.
Check the example
With principal $250,000, nominal rate 6.5%, 30 years and monthly payments, the modeled regular payment is $1,580.17 and interest totals $318,861.22. Adding $200 each month gives 265 payments instead of 360 and modeled interest savings of $97,618.12. These are hypothetical arithmetic results, not a reported borrower outcome, and exclude fees and penalties.
Interest-only and balloon assumptions
The interest-only model charges interest on the remaining balance and accepts extra principal. Its interest payment therefore declines after extra principal; all remaining principal is due at maturity. Actual interest-only products can switch to an amortizing phase, which this model does not implement.
The balloon model uses 30-year amortization for the base payment. At the chosen term, the schedule includes that period’s interest and all remaining principal exactly once. “Final Additional Principal Due” is the lump sum beyond the regular principal and extra payment, not the full final payment. The model rejects terms longer than 30 years.
Interest rate is not APR
APR includes applicable borrowing charges and is distinct from the interest rate. This calculator reports supplied upfront fees and total cash payments, but does not calculate regulatory APR. It does not finance fees or decide which charges a lender must include in APR.
Budget and early-payoff estimates
The budget calculator solves for principal supported by the entered payment under the same fixed-rate assumptions. It is not an affordability or underwriting assessment. Reserve room for taxes, insurance, other debts and non-loan expenses outside this calculation.
The payoff comparison applies extra principal each period. Confirm how the servicer allocates payments and whether a penalty applies. The yearly view covers the full model; the detailed table displays the first 120 periods. Payoff month starts from today and is approximate because no actual payment calendar is entered.