Mortgage calculator
Enter what you are borrowing, the rate and the term. You get the monthly payment, what the loan costs in interest, and how the balance falls year by year.
- Payment without insurance
- $1,581.62
- Total interest
- $129,590
- Total insurance
- $17,500
- Total repaid
- $397,090
- Number of payments
- 240
- Interest as a share of the loan
- 51.8 %
This is an estimate for comparison, not a credit offer. Your lender's figures are the ones that count.
The formula
M = P · i / (1 − (1 + i)^−n), where P is the amount borrowed, i the monthly rate (annual rate ÷ 12) and n the number of monthly payments. Insurance is added as a flat annual percentage of the original amount, billed monthly.
Worked example
Borrow 250,000 over 20 years at 4.5%: i = 0.00375, n = 240, so M = 1,581.59 before insurance. Over the full term you repay 379,581, of which 129,581 is interest.
How to use it
- 1Enter the amount you are borrowing, not the price of the property.
- 2Use the nominal annual rate your lender quotes, not the APR, which includes fees.
- 3Add the insurance rate if your lender bills it separately; leave it at zero otherwise.
Questions people ask
Why is my bank's figure slightly different?
Banks add arrangement fees, guarantee costs and sometimes a different day-count convention. This calculator gives the pure amortisation figure, which is the right basis for comparing two offers.
What happens if I overpay?
Every extra payment reduces the balance that interest is charged on, so the saving compounds. Shortening the term saves far more than reducing the monthly payment.
Last reviewed: 2026-10-20