How can you lower your mortgage rates by reducing mortgage insurance costs? This calculator can help you estimate your monthly payment for private mortgage insurance (PMI) over a range of down payments. If your down payment is at least 20% of the appraisal value of your home, your lender does not require you to obtain mortgage insurance. Mortgage lenders look at the loan-to-value (LTV) ratio of your home before requiring mortgage insurance. You may have to obtain a home appraisal to prove your home's LTV ratio is within the required percentage.