Combination (Piggyback) Mortgage Calculator
A piggyback structure (like 80-10-10) uses a second mortgage to avoid PMI with less than 20% down. Compare it against one loan with PMI.
How the combination (piggyback) mortgage calculator works
A combination or piggyback mortgage splits financing across two loans taken at the same time to dodge private mortgage insurance without a full 20 percent down payment. The classic structure is 80-10-10: a first mortgage for 80 percent of the price, a second mortgage or HELOC for 10 percent, and 10 percent down in cash.
Because the first loan stays at or below 80 percent loan-to-value, no PMI is required. This calculator builds both payments — the larger first and the smaller, usually higher-rate second — and totals them so you can compare against a single loan with PMI.
Worked example: with home price of $400,000, down payment of 10.00% and first mortgage rate of 6.75%, the combination (piggyback) mortgage calculator shows lower monthly payment of Piggyback (80-10-10).
- Piggyback payment
- $2,383.08
- Single loan + PMI
- $2,544.95
- First / second loans
- $320,000 / $40,000
- PMI avoided
- $210.00
| Second mortgage rate | Piggyback | Single + PMI |
|---|---|---|
| 6.00% | $2,315 | $2,545 |
| 8.50% | $2,383 | $2,545 |
| 11.00% | $2,456 | $2,545 |
| 14.00% | $2,549 | $2,545 |
The better choice flips around 14.00% — Piggyback wins on one side, Single + PMI on the other.
The formula
The price is split by the chosen ratios (for example 80/10/10). Each mortgage is amortized separately with its own rate and term using the standard payment formula, then the two monthly payments are added. The second loan typically carries a higher rate because it sits in a riskier lien position.
- The split is treated as fixed percentages of the purchase price; lender programs may require specific ratios like 80/10/10 or 80/15/5.
- The second loan is assumed amortizing at a fixed rate; many real piggybacks are variable HELOCs whose payments move.
- No PMI is included, which is the entire point of the structure — but it requires qualifying for two loans at once.
- Closing costs are generally higher with two loans; those fees are not built into the monthly figures here.
- The second lien usually carries a higher interest rate than the first, reflecting its subordinate claim on the property.
Results are estimates for educational purposes and are not financial advice. Confirm exact figures with your lender or a licensed advisor.
Questions about the combination (piggyback) mortgage calculator
Is a piggyback loan cheaper than just paying PMI?
It depends on the numbers. The second mortgage's higher rate can rival or exceed what PMI would cost, so the math is not automatic.
The advantage is that PMI protects the lender and never builds your equity, while the piggyback's interest at least retires a real debt you own. PMI also eventually cancels; the second loan must be paid off or refinanced.
Can I pay off the second mortgage early to simplify things?
Yes, and many borrowers target the smaller second loan for aggressive prepayment. Clearing it leaves you with a single first mortgage and no insurance, which simplifies your finances and cuts the higher-rate interest.
Check for any prepayment penalty first, and if the second is a HELOC, confirm whether closing it triggers fees. Paying it down also lifts your combined equity position.
What credit profile do I need to qualify for an 80-10-10?
Generally stronger than a single FHA loan requires. Because you are qualifying for two loans simultaneously, lenders scrutinize your debt-to-income ratio and credit score more closely — the second lien is riskier for them.
Expect to need solid credit, documented income, and reserves. Borrowers who cannot clear that bar often find a single loan with PMI is the more realistic path.
Is the Combination (Piggyback) Mortgage Calculator free to use?
Yes. Every calculator on MortgageLoansCalculator is completely free, with no sign-up, login or paywall. Run as many scenarios as you like.
What is a combination (piggyback) mortgage?
A combination or piggyback loan splits financing in two — commonly an 80% first mortgage plus a 10% second, with 10% down (an 80-10-10). It keeps the first mortgage at 80% loan-to-value to avoid PMI without a full 20% down payment.
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