Loan details
Result
Payments and interest are computed period by period from the principal, term and monthly rate using equal-installment or equal-principal; for planning only - the lender's own schedule governs.
Month-by-month schedule
Mortgage details
Commercial rate = 5Y+ LPR plus a spread; enter your own figure.
The housing-fund rate is set by policy and is well below commercial; roughly 2.85% over 5 years.
Result
A combined loan is split into its commercial and housing-fund parts, each priced by its own amount, rate and term, then added together; both parts share the same term here.
Month-by-month schedule
Original loan & payments made
Prepayment estimate
Interest saved = the remaining interest if you kept paying as planned, minus the interest under the new payment or term after the prepayment. The principal you pay now is your own money and is not counted as savings.
Installment details
Result
The nominal fee rate looks low, but you repay principal every month so you hold far less than the full amount on average; the true annualised IRR is usually much higher.
Reference: card statement instalments commonly run about 0.6% per period (roughly 7.2% nominal over 12 periods), which annualises to about 13%.
About this tool
This online calculator brings four common loan-style computations together: a plain loan calculation, a mortgage (commercial / housing-fund / combined), a mortgage prepayment estimate, and an installment-fee and real-APR calculation. All four share one equal-installment / equal-principal engine, compute as you type, show a month-by-month schedule, and export it to CSV - entirely in your browser.
Two repayment methods
Equal installment
Principal and interest are levelled into the same fixed payment every month; early months are mostly interest and later ones mostly principal. Good for stable cash flow. Payment = Principal x monthlyRate x (1+monthlyRate)^n / ((1+monthlyRate)^n - 1).
Equal principal
You repay a fixed amount of principal every month plus interest on the balance, so the payment falls each month and total interest is lower. Monthly principal = Principal / n; interest in month k = remaining balance x monthlyRate.
Installment fee and real APR
How the fee is computed
Instalments usually charge a fee instead of interest. The fee can be given as a rate (of the financed amount) or as an amount, either for the whole term or per period. Fee per period = total fee / periods; payment per period = principal per period + fee per period, where principal per period = amount / periods.
Why the real APR is far above the nominal rate
Take 12 periods at 0.6% per period: the nominal total is only 7.2%, but you are repaying principal every month so your average outstanding balance is roughly half. Solving the payments as an annuity for the IRR and annualising gives a real rate close to twice the nominal one (about 13% here).
FAQ
- Which is cheaper, equal installment or equal principal?
- On total interest alone, equal principal is cheaper because it starts repaying principal sooner, so the balance falls faster. Equal installment costs more but keeps the payment flat and the early burden lower. Choose equal principal if you want the lowest cost and can afford the front load; choose equal installment for a level monthly outlay.
- How is a mortgage rate set?
- Commercial mortgage rates are the 5-year-plus LPR plus a spread that can move; housing-fund rates are set by policy and are clearly lower. A combined loan splits the amount into the two parts, each priced separately and then summed. This tool lets you type any annual rate regardless of its source.
- Does prepaying always save interest?
- Paying down principal reduces the base that later interest accrues on, so it usually saves interest. How much depends on the number of payments already made, how much principal you pay off, and whether you shorten the term or lower the payment - keeping the payment and shortening the term typically saves more than lowering the payment.
- The installment fee looks tiny - why not just compare the nominal rate?
- Because instalments repay principal every month, so on average you hold much less than the face amount. The real cost is the IRR of the payment stream, annualised, which is clearly higher than the nominal fee rate. Compare the real APR this tool reports, not the headline fee rate.
- Are the results accurate?
- All four tools use the standard banking equal-installment / equal-principal formulas and the same installment IRR convention as mainstream online tools, so they are suitable for planning and comparison. Actual disbursement, accrual and any prepayment penalty follow your lender's terms.
About this tool
The loan calculator puts the four most-used loan flows on one page: plain loans and mortgages share the month-by-month interest engine, mortgages additionally distinguish commercial, housing-fund and combined loans, prepayment re-derives the remaining payment or term after some payments are made and reports the interest saved, and the installment-fee tool gives per-period payments and the real IRR by rate or amount.
Everything is computed in your own browser: the formulas ship inside the page scripts, there is no backend and no network request, and your inputs live only in this device's local storage. The server never sees what you calculated, and the page still works offline once loaded.
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