Loan calculator
Monthly payment calculator for mortgages and loans: compare annuity (equal instalment) with equal-principal repayment and get the monthly payment, first and last instalment, total interest, total repayment, a period-by-period schedule and the interest gap between the two methods.
Runs in your browserEvery computation happens in your browser — your data never leaves this device.
Loan parameters
All money is handled in integer cents; interest is charged on the opening balance and the final instalment is adjusted so the balance lands exactly on zero.
Result
5,307.275,307.275,305.190.408333%910,615.121,910,615.12Amortisation schedule
360 instalments in total, showing the first 12
| Period | Payment | Principal | Interest | Balance |
|---|---|---|---|---|
| 1 | 5,307.27 | 1,223.94 | 4,083.33 | 998,776.06 |
| 2 | 5,307.27 | 1,228.93 | 4,078.34 | 997,547.13 |
| 3 | 5,307.27 | 1,233.95 | 4,073.32 | 996,313.18 |
| 4 | 5,307.27 | 1,238.99 | 4,068.28 | 995,074.19 |
| 5 | 5,307.27 | 1,244.05 | 4,063.22 | 993,830.14 |
| 6 | 5,307.27 | 1,249.13 | 4,058.14 | 992,581.01 |
| 7 | 5,307.27 | 1,254.23 | 4,053.04 | 991,326.78 |
| 8 | 5,307.27 | 1,259.35 | 4,047.92 | 990,067.43 |
| 9 | 5,307.27 | 1,264.49 | 4,042.78 | 988,802.94 |
| 10 | 5,307.27 | 1,269.66 | 4,037.61 | 987,533.28 |
| 11 | 5,307.27 | 1,274.84 | 4,032.43 | 986,258.44 |
| 12 | 5,307.27 | 1,280.05 | 4,027.22 | 984,978.39 |
| Total | 63,687.24 | 15,021.61 | 48,665.63 | — |
Method comparison
Equal principal pays more up front but less interest overall; the equal instalment method keeps every payment identical and is easier early on.
910,615.12737,041.21173,573.911,553.84What this tool does
- Estimate a mortgage before you commit: enter the principal, rate and term to see the monthly payment and the total interest.
- Compare equal-instalment and equal-principal repayment on the same loan to see how much interest the faster amortisation saves and what it costs up front.
- Audit the schedule your bank gave you — principal, interest and remaining balance per period are listed so a mismatch stands out immediately.
- See what a rate change does: rerun the same loan at 3.5% instead of 4.9% and read the interest difference straight off the comparison.
Example
Input
Principal 1,000,000 yuan, annual rate 4.9%, 360 months, equal instalment
Output
Monthly payment 5,307.27 yuan, total interest 910,615.12 yuan, total repayment 1,910,615.12 yuan; first-period interest 4,083.33 yuan, final instalment 5,305.19 yuan
The payment from A = P·i/(1−(1+i)^−n) rounds to 5,307.27 yuan; the last instalment differs slightly because the accumulated rounding is settled there.
Frequently asked questions
What is the difference between equal instalment and equal principal?
Equal instalment keeps the payment constant, so interest dominates early and the principal falls slowly. Equal principal repays a fixed amount of principal each period, so the payment decreases over time: heavier at the start, but the loan is repaid faster and the total interest is lower. On 1,000,000 yuan at 4.9% over 30 years, equal instalment costs about 910,615 yuan in interest, and equal principal saves tens of thousands.
How is the monthly payment derived?
Equal instalment uses the annuity formula A = P·i/(1−(1+i)^(−n)), where P is the principal, i the monthly rate (annual rate ÷ 12) and n the number of periods. Equal principal repays P/n of principal each period with interest equal to the opening balance × i. Every interest amount is rounded to the cent and the final period is adjusted so the principal is cleared exactly.
Why does the last instalment differ from the monthly payment?
Because each period’s interest is rounded to the cent, the accumulated rounding is settled in the final period: the tool sets the last principal part to whatever balance remains. The last payment may therefore be a few cents more or less, which guarantees the schedule’s principal parts add up to the loan amount exactly.
What happens at a 0% rate?
At 0% the annuity formula degenerates to principal ÷ months, equal principal repays only principal and every interest amount is zero, so the total interest is 0. For 1,000,000 yuan over 360 periods the payment is 2,777.78 yuan (rounded to the cent) with the balance settled in the final period.
Can I use the result as an actual repayment figure?
It is the mathematically exact result of the standard formulas. Real lenders may not round the per-period interest, may use daily interest or charge fees, and prepayments or rate changes shift the numbers, so the contract and your statement remain the reference.
Keywords：loan calculatormortgage calculatoramortization schedulemonthly paymentequal principaltotal interest贷款计算器房贷月供等额本息等额本金还款计划表总利息