About the Piggyback Loan Calculator (80-10-10)
A piggyback mortgage splits your financing into two loans so the first mortgage stays at 80% of the price and avoids private mortgage insurance (PMI). The classic 80-10-10 is an 80% first mortgage, a 10% second mortgage or HELOC, and 10% down; 80-15-5 and 75-15-10 versions work the same way. The alternative is a single loan for 90% with PMI until the balance falls far enough.
Enter the price, your down payment, the size of the second loan and the rates for each option. The calculator compares monthly payments, works out how many months PMI would last on the single loan (it ends automatically when the scheduled balance reaches 78% of the original value, or at the loan’s midpoint), and totals interest plus PMI over the years you expect to keep the loan.
Piggyback seconds usually carry higher rates, and many are variable-rate HELOCs, so the answer depends on the rate gap, the PMI rate and how long you stay. This tool treats the second loan as a fixed-rate amortizing loan. Closing costs on the second loan, if any, are not included.
With the default inputs, the savings with the cheaper option is $29,790.10. Change any value above to recalculate instantly.
How to use the piggyback loan calculator (80-10-10)
- 1Enter the home price, your down payment percentage and the second loan percentage.
- 2Enter the first mortgage rate and term, and the second loan rate and term.
- 3Enter the rate and PMI rate quoted for a single loan at the same loan-to-value.
- 4Set how many years you expect to keep the loan.
- 5Compare monthly payments, PMI months and total cost to see which option wins.
Formula and method
Both options borrow the same total (price minus down payment), so principal repaid is the same and the cost comparison is interest plus PMI over the years you keep the loan. The piggyback first and second loans are amortized separately at their own rates and terms; the single loan is amortized at its own rate and charged PMI of (PMI rate × loan) ÷ 12 per month.
Following the Homeowners Protection Act, PMI ends automatically when the scheduled balance first reaches 78% of the original value, or at the midpoint of the term if that comes first. Interest is calculated month by month; a second loan with a shorter term stops costing interest once it is repaid. Closing costs and tax effects are not included.
- second
- Second mortgage amount (second % × price)
- n
- First mortgage term in months
- H
- Years you expect to keep the loan
Worked examples
$500k home, 80-10-10 vs 90% loan with PMI
The piggyback splits $450,000 into a $400,000 first mortgage at 6.75% ($2,594.39) and a $50,000 second at 8.5% over 15 years ($492.37). The single $450,000 loan at 6.875% costs $2,956.18 plus $225 of PMI for 114 months. Over 10 years the piggyback costs about $285,614 in interest versus $315,404 of interest and PMI, saving about $29,790.
Cheap PMI, costly 30-year second, 20-year horizon
When the single loan gets the same 6.75% rate, PMI is only 0.3% ($112.50 a month for 112 months) and the second loan is a 10% 30-year loan, the single loan wins: about $517,274 of interest and PMI over 20 years versus $537,111 of interest for the piggyback.
Frequently asked questions
What is an 80-10-10 loan?+
It is a piggyback structure: an 80% first mortgage, a 10% second mortgage or HELOC, and a 10% down payment. Keeping the first loan at 80% loan-to-value avoids private mortgage insurance on a conventional loan.
Is a piggyback loan better than paying PMI?+
It depends on the second loan’s rate, the PMI rate and how long you keep the loan. PMI ends once the balance reaches 78% of the original value, while the second loan’s higher rate lasts until it is paid off, so short PMI periods often favour the single loan.
Can I refinance or pay off the second loan early?+
Usually yes. Paying off the second mortgage early cuts its interest cost, and many borrowers refinance both loans into one once they have 20% equity. Check for prepayment penalties or HELOC early-closure fees.
Why do lenders charge more for the second mortgage?+
The second lien is repaid only after the first mortgage in a foreclosure, so it carries more risk. Rates on piggyback seconds and HELOCs are therefore usually higher than on first mortgages, and many HELOC rates are variable.
Can a piggyback loan help with jumbo limits?+
Yes. Some buyers use an 80-10-10 to keep the first mortgage under the conforming loan limit and avoid jumbo loan pricing, with the second loan covering the rest.
Results are estimates for educational purposes and are not financial advice. Rates, fees and terms vary — confirm with your lender or a licensed advisor before making decisions.