Mortgage calculator

Usually a different interest convention, not a mistake. This page takes the monthly rate as annual rate / 12, rounds each period's interest to the cent, and settles the remaining principal in full on the last period (so the final payment can be a few cents or yuan above the regular one). Banks may compute interest on actual days (each month has a different count) or apply their own rounding rules, and across hundreds of periods a gap of tens of yuan is normal. For exact reconciliation use the schedule issued by your bank; this page's value is comparing options against each other.

That is the final-period adjustment, not a bug. Each period's interest and principal are rounded to the cent, and over hundreds of periods a residue of cents or yuan accumulates; the last period settles the remaining principal in one go, so its amount differs slightly from the regular payment. Conversely a final payment smaller than the regular one (also common) is the same residue effect. The result explicitly flags whether the last period was adjusted and by how much.

Pure savings: shortening the term wins, because principal leaves the interest base earlier. For example, 1,000,000 over 30 years at 4.9%, prepaying 100,000 after the 12th period: interest saved by shortening is roughly three times that of lowering the payment. But if the payment already makes you afraid of losing your job, lowering it buys monthly cash-flow safety, which is also worth something. Before signing, always confirm with the bank: which handling is the default, whether there is a penalty or fee, and whether you get a new amortization schedule after the recalculation.

Zero rate takes its own branch: payment = principal / periods, total interest is exactly 0, no division by zero, no NaN. A term of 0, negatives or non-numbers are rejected in place - you never get a 'looks normal' result. Tiny inputs like 1 yuan over 1 period compute normally (principal 1.00, interest 0.00). And if a payment cannot even cover the current period's interest (debt snowballing), the page says outright that no amortization schedule can be produced - it will not grind out a fake one.

No. The CSV carries a UTF-8 BOM, so Excel (Windows included) reads Chinese correctly; amounts are written as plain two-decimal numbers without thousands separators, so Excel cannot split one figure into two cells at a comma. The file is generated locally in your browser and downloaded directly - it never passes through the server.