80/10/10 Piggyback Loan Calculator
The 80/10/10 piggyback uses a second mortgage to bridge the 20% down payment gap and avoid private mortgage insurance (PMI). For high-cost markets it often costs less monthly than a single 90% LTV loan with PMI.
How 80/10/10 Structures Work
First mortgage at 80% LTV avoids PMI under standard conforming guidelines. The 10% second mortgage (typically a HELOC) covers what would otherwise be down payment. Borrower contributes the final 10% in cash.
When Piggyback Beats Single Loan + PMI
PMI on a $650K 90% LTV loan at 0.75% annual costs about $365/month. A 10% piggyback HELOC at 9.5% costs about $545/month. The piggyback wins only if the HELOC can be paid down aggressively or the first-loan rate savings (from staying under 80% LTV) exceeds the higher second rate.
Risks Specific To Piggyback
Variable-rate seconds (HELOCs) can reset higher in rising-rate environments. Pre-2008 era saw mass piggyback defaults when seconds reset. Today's piggyback is safer (smaller balances, tighter underwriting) but still requires a payoff plan rather than minimum payments.
Source: CFPB Mortgage Origination Guidance; Freddie Mac PMI cancellation rules. Last updated: May 2026.