Second Mortgage Calculator
Calculate your combined first and second mortgage payments. See your combined LTV, total interest on both loans, and how much equity you can tap.
How does adding a HELOC (interest-only during draw) compare to a fixed HEL (Home Equity Loan) for borrowing $60,000?
Three ways to access $60,000 of your home's equity. Cash-out refi replaces your first mortgage entirely.
How to Use This Second Mortgage Calculator
Enter your home value, first mortgage details, and the second mortgage you're considering to see your combined payment, combined LTV, and total interest costs.
Combined LTV (CLTV)
The key metric lenders use is Combined Loan-to-Value (CLTV): total debt divided by home value. Most lenders cap this at 80–85%. The calculator warns if your proposed second mortgage would exceed this limit.
Second Mortgage Rate
Second mortgages carry higher rates because they're in "second lien position" — if you default, the first lender gets paid first, making second mortgages riskier. Expect rates 1–2% above current first mortgage rates.
When to Choose a Second Mortgage vs. Cash-Out Refinance
A second mortgage preserves your existing first mortgage rate — critical if you locked in a rate below current market rates. If current rates are higher than your first mortgage rate, a second mortgage is almost always more cost-effective than a cash-out refinance.
Second Mortgage Payment Formula
Second Monthly Payment = P2 × [r2(1+r2)^n2] / [(1+r2)^n2 - 1]
Combined Monthly = First Payment + Second Payment
CLTV = (First Balance + Second Amount) ÷ Home Value × 100
Max Second Mortgage = (Home Value × 0.85) − First Balance
Example: $450,000 home, $280,000 first mortgage (6.75%, 27 yrs remaining) = $1,853/mo. Add $60,000 second at 8.5% for 10 years = $744/mo. Combined = $2,597/mo. CLTV = 75.6%.
Example: Home Equity Loan for Renovation
The Nguyens Add a Primary Suite Addition
Their home has appreciated to $450,000, with $280,000 remaining on a 6.75% mortgage. They want $60,000 for a primary suite addition — but don't want to touch their 6.75% rate.
| Home Value | $450,000 |
| First Mortgage Balance | $280,000 at 6.75% |
| First Monthly Payment | $1,853 |
| Second Mortgage Amount | $60,000 at 8.5% |
| Second Term | 10 years |
| Second Monthly Payment | $744 |
| Combined Monthly | $2,597 |
| CLTV | 75.6% (well under 85% limit) |
| Total Second Mortgage Interest | $29,280 |
If they had done a cash-out refinance of $340,000 at current 7.25% rates, their monthly payment would be $2,320 — apparently less, but they'd lose their favorable 6.75% rate on the entire $280,000 balance and pay far more interest over the remaining loan life.