Calculating monthly mortgage insurance on a conventional loan is best handled directly with the mortgage company whom you’re hiring to do your purchase preapproval and/or refinance loan with. However, to have a general understanding of how mortgage insurance works, know that it is required for any loan with less than 20% down.
Plan on on using a calculation of approximately 70 basis points or rather .70% of the loan amount. Using a loan for $300,000-that equates to $2100 per year, divided by 12 representing 12 months would equal approximately $175 per month. 70 basis points would be about right if your credit score is 700 or higher. If your credit score is under 700 plan on using a factor of 90 basis points. Same math applies on how to compute the monthly mortgage insurance payment.
When comparing the conventional loan to an FHA loan in almost every circumstance the conventional loan does contain lower monthly mortgage insurance. Talk to a qualified mortgage professional about what loan program makes sense given the down payment factor as well as the long-term payment affordability.