Mortgage calculator
Enter the house price, down payment, annual rate and term to get the loan amount, monthly payment, total interest, total repayment and total cost of buying — plus an annuity versus equal-principal comparison, the repayment schedule and a rate sensitivity table.
Runs in your browserEvery computation happens in your browser — your data never leaves this device.
Mortgage inputs
All money is integer cents; interest is rounded to the cent on the opening balance and the final instalment is trued up so the principal column adds up to the loan.
Result
900,000.002,100,000.0070.00%9,547.559,547.559,548.920.300000%1,337,119.373,437,119.374,337,119.3763.67%19,095.10Repayment method comparison
Equal principal pays more up front and less interest overall; the equal instalment method keeps every payment identical and is gentler early on.
1,337,119.371,137,150.00199,969.372,585.79Rate sensitivity
One percentage point either side of the current rate, all on an equal-instalment basis.
| Annual rate | Monthly payment | Total interest |
|---|---|---|
| 2.60% | 8,407.13 | 926,568.99 |
| 3.10% | 8,967.34 | 1,128,244.77 |
| 3.60% | 9,547.55 | 1,337,119.37 |
| 4.10% | 10,147.17 | 1,552,978.14 |
| 4.60% | 10,765.53 | 1,775,592.05 |
Repayment schedule
360 instalments in total; only the first 12 are listed.
| Period | Payment | Principal | Interest | Balance |
|---|---|---|---|---|
| 1 | 9,547.55 | 3,247.55 | 6,300.00 | 2,096,752.45 |
| 2 | 9,547.55 | 3,257.29 | 6,290.26 | 2,093,495.16 |
| 3 | 9,547.55 | 3,267.06 | 6,280.49 | 2,090,228.10 |
| 4 | 9,547.55 | 3,276.87 | 6,270.68 | 2,086,951.23 |
| 5 | 9,547.55 | 3,286.70 | 6,260.85 | 2,083,664.53 |
| 6 | 9,547.55 | 3,296.56 | 6,250.99 | 2,080,367.97 |
| 7 | 9,547.55 | 3,306.45 | 6,241.10 | 2,077,061.52 |
| 8 | 9,547.55 | 3,316.37 | 6,231.18 | 2,073,745.15 |
| 9 | 9,547.55 | 3,326.31 | 6,221.24 | 2,070,418.84 |
| 10 | 9,547.55 | 3,336.29 | 6,211.26 | 2,067,082.55 |
| 11 | 9,547.55 | 3,346.30 | 6,201.25 | 2,063,736.25 |
| 12 | 9,547.55 | 3,356.34 | 6,191.21 | 2,060,379.91 |
What this tool does
- Check affordability before a viewing: a 3,000,000 home with a 30% down payment at 3.6% over 30 years costs about 9,547.55 a month and about 1,337,119.37 in interest.
- Compare repayment methods: on the same loan the equal-principal plan costs 2,585.79 more in the first month but saves roughly 200,000 of interest over 30 years.
- Stress-test the rate: the sensitivity table lines up the monthly payment and total interest one percentage point either side of your rate.
- Reconcile a bank quote: the schedule lets you check that the first month’s interest equals loan × monthly rate, and shows the total cost of buying.
Example
Input
House price 3,000,000, 30% down payment, 3.6% annual rate, 30-year term, equal instalment
Output
Down payment 900,000.00; loan 2,100,000.00; loan to value 70.00%; monthly payment 9,547.55; first instalment 9,547.55 (interest 6,300.00); last instalment 9,548.92; monthly rate 0.300000%; total interest 1,337,119.37; total repayment 3,437,119.37; total cost 4,337,119.37
The first month’s interest of 6,300.00 is 2,100,000 × 0.3% — the quickest sanity check on the result. The final instalment is 1.37 higher than the monthly payment because rounding to the cent is trued up when the balance is cleared.
Frequently asked questions
How much should I put down?
The tool accepts anything from 0% up to (but not including) 100%. A smaller down payment means a bigger loan, so both the monthly payment and the total interest rise. What you can actually borrow also depends on local rules, the bank’s valuation and your income — lenders usually want the payment to stay under 50% of income, which is exactly what the income reference row assumes.
Equal instalment or equal principal?
Equal instalment keeps every payment the same, which is easier early on but costs more interest. Equal principal repays a fixed amount of principal each month with shrinking interest, so the first payments are highest and then fall, and the total interest is lower. On a 3,000,000 home with 30% down at 3.6% over 30 years that is 1,337,119.37 versus 1,137,150.00 in interest — a 199,969.37 difference.
How much does the rate matter?
On a 2,100,000 loan over 30 years, half a percentage point adds roughly 500 to the monthly payment (9,547.55 at 3.6%, 10,147.17 at 4.1%) and about 216,000 to the total interest. That is why the sensitivity table is separate: see whether you can absorb a rate rise before committing.
Can it model overpayments, floating rates or a mixed loan?
This tool assumes a fixed rate with level instalments; it does not model rate resets, a combined commercial plus provident-fund loan, or overpayments. If you want to see how extra monthly payments cut the term and the interest, use the loan amortization tool, which supports exactly that.
Why are taxes and agent fees missing?
The total cost of buying here is the price plus the loan interest, covering the borrowing only. Stamp duty, transfer taxes, agent commission and renovation vary hugely by city and property type, so they are left to a separate estimate; the numbers here are a mathematical estimate, not investment advice.
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