How to Calculate Your PMI Monthly Cost Before Your Lender Does It for You

What PMI Actually Is and Why the Rate Varies So Much

Private mortgage insurance protects the lender, not the borrower. When a buyer puts down less than 20% of the purchase price, the lender carries higher default risk. PMI transfers a portion of that risk to a third-party insurer. The borrower pays the premium.

The rate is not arbitrary. Lenders and PMI providers price the premium based on three primary variables.

Loan-to-value ratio (LTV). A borrower putting down 5% on a $500,000 home carries an LTV of 95%. That borrower will pay a higher PMI rate than someone putting down 15%, who carries an LTV of 85%. The closer LTV is to 100%, the higher the perceived default risk.

Credit score. A FICO score of 760 or above will attract rates near the bottom of the range, typically 0.19% to 0.45% annually. A score between 620 and 639 can push rates above 1.50%. That difference is not marginal.

Loan type and term. A 30-year fixed loan carries a different rate than a 15-year fixed. Adjustable-rate mortgages introduce additional pricing complexity.

Fannie Mae publishes PMI rate tables that lenders use as a baseline. The actual rate on any given loan depends on which PMI provider the lender uses, but Fannie's tables give a reliable approximation for pre-closing calculations.

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The Formula

PMI monthly cost follows a single calculation.

Annual PMI cost = Loan amount × PMI rate

Monthly PMI cost = Annual PMI cost ÷ 12

That is the complete formula. The challenge is knowing which PMI rate to apply, because lenders do not always disclose it explicitly on early loan estimates.

To find the rate, take the PMI line item on any Loan Estimate disclosure and divide by the original loan amount. Multiply by 12 to annualize it. That gives you the annual rate, which you can then compare against published benchmarks.

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Worked Example 1: The Mid-Range Buyer

Scenario. A buyer purchases a home for $450,000. The down payment is $22,500, which is exactly 5%. The loan amount is $427,500. The buyer's FICO score is 720. The lender quotes a PMI rate of 0.58% annually.

Calculation.

• Annual PMI cost: $427,500 × 0.0058 = $2,479.50
• Monthly PMI cost: $2,479.50 ÷ 12 = $206.63 per month

This buyer will pay $206.63 per month until the loan balance reaches 80% of the original appraised value, which is $360,000. At a standard amortization schedule on a 30-year fixed at 6.85%, that crossover occurs approximately 9.5 years into the loan.

Total PMI paid over that period: approximately $23,500.

Now run the same scenario with a 10% down payment. The loan drops to $405,000. LTV moves to 90%. The PMI rate falls to approximately 0.41% at the same credit score.

• Annual PMI cost: $405,000 × 0.0041 = $1,660.50
• Monthly PMI cost: $1,660.50 ÷ 12 = $138.38 per month

The borrower reaches the 80% LTV threshold faster because the starting balance is lower. PMI cancels in roughly 5.8 years. Total PMI paid: approximately $9,635.

The difference between 5% down and 10% down on this purchase is $13,865 in PMI costs, plus the additional $22,500 of down payment capital deployed. Whether that tradeoff favors the larger down payment depends on the opportunity cost of that $22,500, which the CalcMoney mortgage calculator models directly.

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Worked Example 2: The High-Credit Borrower Who Still Overpays

Scenario. A buyer purchases a home for $750,000. The down payment is $75,000, representing 10% down. Loan amount is $675,000. FICO score is 780. The lender's Loan Estimate shows a monthly PMI line of $321.75.

Most buyers accept that number. Fewer verify it.

Verification calculation.

• Annual PMI: $321.75 × 12 = $3,861.00
• Implied rate: $3,861.00 ÷ $675,000 = 0.5720%

For a borrower with a 780 FICO at 90% LTV, the Fannie Mae rate table suggests a rate closer to 0.38% to 0.44% annually, depending on the loan product. At 0.41%:

• Annual PMI cost: $675,000 × 0.0041 = $2,767.50
• Monthly PMI cost: $2,767.50 ÷ 12 = $230.63 per month

The lender is pricing PMI at $91.12 per month above the benchmark range. That is $1,093 per year. Over a six-year PMI window, the total excess charge reaches $6,558.

This happens. PMI providers vary. Some lenders pass through more expensive PMI providers without explanation. A buyer who arrives at closing with this calculation in hand can ask for the PMI provider's rate sheet and request a re-quote from an alternative provider. Many lenders will accommodate that request. Most borrowers never make it.

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How to Find Your Actual PMI Rate Before the Loan Estimate

Lenders will not proactively give you the rate in percentage terms. They will quote a dollar amount. That is not sufficient for comparison purposes.

Three ways to find your PMI rate before closing.

Ask directly. Request the annual PMI rate as a percentage of the loan amount. Frame it as a verification step. Any competent loan officer will provide it.

Use Fannie Mae's rate tables. The Loan-Level Price Adjustment and PMI factor tables are publicly available. Look up your LTV bucket and credit score band. Cross-reference against your lender's dollar figure.

Use the reverse calculation. Take the monthly dollar amount from the Loan Estimate. Multiply by 12. Divide by the loan amount. That is your annual rate. Compare it to the Fannie table.

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When PMI Terminates and How to Accelerate It

The Homeowners Protection Act of 1998 requires automatic PMI cancellation when the loan balance reaches 78% of the original purchase price on conforming loans. Borrowers can request cancellation at 80% LTV if the loan is current and the property value has not declined.

Two strategies accelerate the cancellation date.

Extra principal payments. An additional $300 per month on a $427,500 loan at 6.85% moves the 80% LTV threshold from 9.5 years to approximately 6.7 years. That saves roughly $7,100 in PMI premiums.

Appreciation-based reappraisal. If the property appreciates substantially, the borrower can request a new appraisal and ask the lender to terminate PMI based on current value rather than original purchase price. The lender will require an LTV of 80% or below on the current appraised value. There is typically a minimum period of 24 months before this request is considered. An appraisal costs $300 to $600. On a property that appreciated 12% in two years, the math on PMI termination is straightforward.

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PMI Alternatives Worth Modeling Before You Sign

PMI is not the only structure available to buyers under 20% down.

Lender-paid PMI (LPMI). The lender absorbs the PMI premium in exchange for a higher interest rate, typically 0.25% to 0.75% above the market rate. This makes sense only if the borrower plans to sell or refinance before the break-even point on the rate differential.

Piggyback loans (80/10/10 structure). The borrower takes a first mortgage for 80% of the purchase price, a second mortgage for 10%, and puts down 10%. No PMI applies because the first mortgage LTV is exactly 80%. The second mortgage typically carries a higher rate, often 1.5% to 2.5% above the first. The calculation of whether this beats PMI depends on the second mortgage rate and the expected PMI cancellation date.

Both alternatives require specific numbers to evaluate properly. A single rate assumption in either direction changes the answer.

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Run the Numbers Before the Lender Runs Them for You

PMI is a line item that most buyers accept without calculation. It is also a line item with a defined formula, published rate benchmarks, and a predictable termination timeline. That is enough information to verify every figure on a Loan Estimate and negotiate from a position of accuracy rather than assumption.

The CalcMoney mortgage calculator includes a full PMI projection, showing monthly cost, total PMI paid over the loan term, the estimated cancellation date, and the impact of extra principal payments on that timeline. Input your loan amount, down payment, credit score range, and projected rate to see the complete cost picture before any lender conversation.

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Model your full mortgage cost including PMI at CalcMoney →