The row-by-row loan schedule that doesn't drift by the last payment

Because the standard payment formula only pays a loan to exactly zero in infinite-precision arithmetic. Once every payment is rounded to the cent, rounding compounds across dozens or hundreds of rows, so the last row almost never has exactly the standard payment's worth of principal left. This tool recomputes the final row as the remaining balance plus that row's interest, so it ends at exactly zero instead of a few cents or dollars off — and reports the delta explicitly rather than hiding it.

Monthly compounding (rate ÷ 12 applied once per payment) is the norm for fixed-rate mortgages. Daily accrual — interest computed on the actual number of days since the last payment — is how most HELOCs, many auto loans, and most private student loans actually work. Check your note or disclosure statement; it usually says "interest accrues daily" or gives a per-diem rate if it is a daily-accrual loan. Guessing wrong produces a plausible but genuinely different schedule, not just a rounding difference.

Because daily accrual depends on how many days are actually in each period — 28 to 31 for a monthly payment, and one extra during a leap year if February falls inside the period. A real loan has a start date, so this tool reads those day counts straight off the calendar instead of asking you whether your term happens to cross a leap year. Only a hypothetical loan with no dates falls back to an assumed day-count basis (30/360, actual/365, or actual/actual) — and in that case, because every period is assumed the same length, all three bases and monthly compounding actually produce the same numbers. The conventions only diverge once real dates introduce months of different lengths.

It depends on your balance, rate, and how far into the loan you are — there is no fixed rule of thumb, which is why this needs an actual recalculation rather than an estimate. Supply `extraPrincipal` as either a one-off amount at a specific payment number or a recurring amount starting from a given payment number, and the tool returns the schedule both with and without it, so the periods and interest saved are explicit rather than guessed.

The Homeowners Protection Act requires automatic termination once your balance reaches 78% of the home's original value, on the original amortization schedule. You can also request cancellation earlier, at 80%. This tool models both thresholds against your ACTUAL balance (including any extra principal you have paid), which can put its cancellation point earlier than your servicer's — the servicer is legally permitted to use the original schedule instead unless your payment history qualifies you for early cancellation. Confirm the exact date with your servicer, especially if you have overpaid.

This is a real condition called negative amortization: if a payment does not exceed the interest charged in the very first period, the balance can never shrink, and a schedule would run forever. This tool refuses to produce a schedule in that case and states the minimum payment that would actually make progress on principal, rather than silently returning a table that never reaches zero.

No — "biweekly" here means paying half of the standard monthly payment every 14 days. Since a year has 26 fourteen-day periods rather than 24 half-months, that works out to 13 full monthly payments a year instead of 12. The extra payment, not a rate discount, is what shortens the payoff.

No. This is a planning estimate built from the numbers you supply. It does not know about an ARM's future rate changes, escrow, late fees, or a servicer's specific rounding or PMI-timing rules. Use it to sanity-check a statement or plan ahead of one, not to replace one.