Mortgage insurance is required for all home purchases with down payments less than 20% of a property’s value. The insurance protects mortgage lenders should the borrower be unable to make payments and default on the mortgage. The insurance cost is included in your mortgage payments, but you should still know how much it costs. Our Mortgage CMHC Mortgage Insurance Calculator helps you determine the cost of your mortgage insurance. Enter your down payment amount and the length of time for your mortgage repayment to calculate the costs of your insurance premium.