How to use
- Enter the home price and your down payment, either as a % of price or an amount. The loan is the price minus the down payment.
- Enter the interest rate and the loan term in years. The monthly principal-and-interest payment, loan-to-value ratio and total interest appear instantly.
- Add yearly property tax and home insurance to see the full monthly payment (they are divided by 12), and an extra payment per month to see how much sooner the loan ends and how much interest you save.
- Set the first payment date to get payoff dates, and copy the yearly amortization table into a spreadsheet if you like.
How it’s calculated
P = loan amount, r = monthly rate (annual rate ÷ 12), n = number of monthly payments.
| Item | Formula |
|---|---|
| Loan amount | home price − down payment |
| Loan-to-value (LTV) | loan amount ÷ home price × 100 |
| Principal & interest | P × r(1+r)ⁿ ÷ ((1+r)ⁿ − 1) |
| Extra payments | Each month, everything above that month’s interest — plus the extra amount — reduces the balance; the loan ends when the balance reaches zero |
| Monthly payment | principal & interest + (property tax + insurance per year) ÷ 12 |
The scheduled payment stays the same when you pay extra; the term gets shorter instead. A 0% rate simply divides the loan by the number of months.
Example: 400,000 home, 20% down, 6.5%, 30 years
With 4,800 a year in property tax and 1,500 in insurance:
| Item | Result |
|---|---|
| Loan amount / LTV | 320,000 / 80% |
| Principal & interest | 2,022.62 a month |
| Monthly payment with tax & insurance | 2,547.62 |
| Total interest | 408,142.36 |
| Paying 200 extra each month | paid off in 23 years 5 months (6 years 7 months sooner) |
| Interest saved | 105,428.67 |
An extra 200 a month — about 10% of the payment — cuts total interest by roughly a quarter.
Things to keep in mind
- Results are for reference only. Lenders may differ in how they accrue interest and round payments, and adjustable-rate loans change payments when the rate resets.
- On a conventional loan with less than 20% down, lenders usually require private mortgage insurance (PMI), which is not included here. HOA dues and closing costs are not included either.
- Real property tax and insurance bills change over time; your escrow payment can go up or down each year.
- Check whether your loan has a prepayment penalty before paying extra. For other loan types, try the loan calculator.
FAQ
What is a good loan-to-value ratio?
Lenders generally offer better terms at lower LTV. At 80% or below — a 20% down payment — conventional loans typically don’t require PMI.
Should I pay extra or invest the money instead?
Extra principal earns you a guaranteed “return” equal to your mortgage rate. Whether that beats investing depends on your rate, taxes, emergency savings and risk tolerance.
Is anything I enter saved or sent anywhere?
No. All calculations run in your browser.