How to use this mortgage calculator
- Pick the country. The currency, compounding method and local costs change to match: PMI for the US, stamp duty for the UK, mortgage default insurance for Canada.
- Enter the price and down payment, as an amount or a percentage.
- Set the loan term in years and the annual interest rate from your lender’s quote.
- Add yearly property tax, yearly insurance and any monthly HOA, condo or service charge, or leave them at zero.
- Add an optional extra monthly payment.
- Download the yearly or monthly schedule as a CSV file.
How the mortgage payment formula works
A fixed-rate mortgage is repaid in equal monthly instalments. The calculator finds that instalment with the standard amortization formula:
In the US and UK, the monthly rate is the annual rate divided by 12. As on a lender’s schedule, payments and monthly interest are rounded to the cent, and the final payment absorbs the leftover cents.
Worked example (US)
A $400,000 home with 10% down ($40,000) needs a $360,000 loan. At 6.5% for 30 years, r = 0.065 ÷ 12 = 0.0054167 and n = 360. The formula gives $2,275.44 a month for principal and interest.
Add property tax of $4,800 a year ($400 a month), insurance of $1,500 a year ($125) and PMI at 0.5% of the loan ($150), and the first-month total is $2,950.44. PMI stops after 109 payments, when the balance drops to $312,000, which is 78% of the original price. Over the full term you pay $459,164.00 in interest.
Adding $200 a month to principal clears the loan 73 months early and saves $108,918.75 in interest. PMI still ends automatically after 109 payments, the scheduled date, but you could ask your servicer to cancel it at 80% after 64 payments.
What changes in Canada and the UK
Canada. Fixed rates are compounded semi-annually, so r = (1 + annual rate ÷ 2)1/6 − 1: at 4.5%, 0.3715% a month rather than 0.375%. With less than 20% down, a default insurance premium is added to the loan: 2.80%, 3.10% or 4.00% depending on the down payment (4.50% if part of it is borrowed), plus 0.20% for amortizations over 25 years. Those longer terms are open only to first-time buyers and new builds, and insured loans cannot exceed 30 years. A $600,000 home with 10% down carries a $16,740 premium, so the loan becomes $556,740 and the payment at 4.5% over 25 years is $3,081.41. In Ontario, Quebec and Saskatchewan, sales tax on the premium is due at closing.
United Kingdom. Stamp Duty Land Tax is paid once, on completion, so it is shown separately. The calculator uses the England and Northern Ireland bands from April 2025 and does not add the 2% surcharge for buyers who are not UK residents. A first-time buyer paying £350,000 owes £2,500, and a £315,000 mortgage at 4.5% over 25 years costs £1,750.87 a month. Scotland and Wales charge their own taxes instead.
Key features
- US, UK and Canada modes with the correct currency format and compounding.
- PMI that ends on the scheduled 78% date, plus the earliest 80% cancellation request when you prepay.
- Extra-payment savings in both interest and months.
- Yearly or monthly amortization table, balance chart and CSV download.
Practical use cases
Comparing terms. At the same 6.5% rate, a 15-year loan on $360,000 costs $3,135.99 a month, $860.55 more than the 30-year loan, but total interest falls from $459,164.00 to $204,477.16.
Planning a UK remortgage. When a fixed deal ends, enter your outstanding balance as the price with no deposit, plus the remaining term and new rate.