10-Year Second Mortgage Calculator

What a second mortgage is and what the 10-year term changes

A second mortgage is a fixed amount borrowed against the equity in a home while a first mortgage stays in place. If the property is ever sold short, the first lender is paid before the second, which is why second liens carry higher rates than first mortgages. The CFPB's second mortgage explainer covers the basic structure: a lump sum, a fixed schedule, and the home as collateral.

The 10-year term is the popular middle choice. It is short enough that total interest stays bounded, and long enough that the payment fits a working budget next to the first mortgage. On the example used through this page, a $50,000 second mortgage at 8.75% over 10 years, the payment is $626.63 a month and the interest bill over the decade is $25,196.05. The same amount over 15 years would cost $499.72 a month but $39,950.38 of interest, so the shorter term buys a lower total price at the cost of $126.91 more each month.

The widget below computes the payment, the split between interest and principal, an APR that folds in the origination fee, the combined loan-to-value the two mortgages create, and the payoff date under extra payments.

The payment on a $50,000 second mortgage, worked step by step

The payment comes from one formula: the balance times the monthly rate, divided by one minus (one plus the monthly rate) raised to the power of minus 120. The monthly rate is 0.0875 / 12 = 0.00729167. Feed in the example numbers and the payment is $626.63, fixed for all 120 months.

The split inside the payment moves every month. In month one the interest piece is 50,000 x 0.00729167 = 364.58, so the principal piece is 626.63 - 364.58 = 262.05. By month 60 the balance has fallen to $30,766.53 and interest takes only 224.34 of the payment, leaving 402.29 for principal. The final payment is almost all principal: 626.63 - 4.54 = 622.09.

Total payments come to $75,196.05, so interest is $25,196.05, which is 33.5% of everything paid. The pace of the payoff matters when comparing against a home equity line of credit, where the minimum payment in the draw period can sit near the interest alone and the balance never falls.

Combined loan-to-value: the ceiling lenders apply to second liens

Lenders judge a second mortgage by combined loan-to-value, or CLTV: the first mortgage balance plus the new second mortgage, divided by the home's value. Most programs stop between 80% and 85%. The example home is worth $400,000 with a $290,000 first mortgage, so adding a $50,000 second puts total debt at $340,000 and CLTV at 85.0%, the edge of the box. Borrow more and the quote usually disappears or the rate rises.

The table shows the lever most borrowers miss: the CLTV cap is about the sum, not the new loan alone. A borrower who pays the first mortgage down to $250,000 can carry the $50,000 second at exactly 75.0%, while a borrower still at $300,000 sits at 87.5% and is turned away at the same loan size. Equity also moves with the market, so the value figure a lender uses is a fresh appraisal or an automated valuation, not the purchase price from years ago.

Enter the home value and the first mortgage balance in the widget and the CLTV line updates with the loan amount, which is the fastest way to see how much room is left under a cap.

Why the rate on a second mortgage runs higher

Second liens price above first mortgages for two reasons. The lender stands behind the first lender in any recovery, and the loans are smaller, so fixed servicing costs spread over less money. The Freddie Mac Primary Mortgage Market Survey tracks the 30-year first-mortgage average, 7.24% for the week ending October 29, 2026, and second lien quotes typically sit one to three points above the first mortgage market at the same moment.

The payment is sensitive to both the rate and the size, so the table below prices three realistic loans on the same 10-year schedule.

Notice how the rate and the size pull in opposite directions here: the biggest loan carries the lowest rate, because lenders tier pricing by CLTV and credit rather than by amount alone. The only quote that counts is the one on your Loan Estimate, which separates the note rate from fees and credits.

Extra payments, biweekly pay and the 15-year alternative

Extra principal works on a second mortgage the way it works anywhere: each dollar sent early stops accruing interest for the rest of the schedule. On a 10-year term there is less time left for interest to compound than on a 30-year loan, but the acceleration is still easy to see on the example loan.

The biweekly plan splits each month's payment in half and pays every two weeks, so 26 half payments deliver 13 full payments a year. The extra principal works out to 626.63 / 12 = 52.22 a month on average, and the loan ends 13 months early. Tell the servicer in writing that extra money goes to principal, not to next month's payment, and check the note for a prepayment penalty before setting up any plan.

The 15-year row is the honest alternative for a stretched budget: $126.91 less per month buys a longer decade of interest. If cash flow is tight now but expected to rise, the 15-year term plus voluntary extra payments beats the 10-year term plus missed payments.

Fees, the APR line and what lands in your account

Second mortgages carry closing costs: an origination fee, an appraisal or valuation fee, title work and recording. Suppose the $50,000 loan charges a 2% origination fee, which is 50,000 x 2% = 1,000, and the other costs are waived. You sign for $50,000 but receive $49,000, and the payment is still computed on the full $50,000.

The APR exists to expose that gap. Solving for the rate that prices a $626.63 payment on a $49,000 amount over 120 months gives 9.22%, a full 47 basis points above the 8.75% note rate. On small second mortgages the effect is bigger in percentage terms: the same 2% fee on a $20,000 loan moves the APR by roughly the same absolute amount, but the loan retires in the same 120 months over a much smaller payment, so compare APR to APR rather than rate to rate.

The CFPB explains the rate versus APR distinction for exactly this situation. When quotes differ by a quarter point of rate but a point of fees, the lower-rate quote can cost more over 10 years.

Second mortgage or HELOC: how the payment math differs

A home equity line of credit and a second mortgage borrow against the same equity, but the arithmetic behaves differently. The second mortgage on this page is a fixed amount at a fixed rate from day one: $626.63 a month, 120 months, done. A HELOC is a revolving line, usually with a variable rate, a draw period where payments can cover little more than interest, and then a repayment period where the payment jumps to amortize the balance over the remaining years.

Three practical consequences follow. First, the second mortgage costs more per month from the start but guarantees the payoff date. Second, the HELOC rate moves with the market, so the payment is a moving target even before the repayment period begins. Third, interest deductibility follows the money, not the loan name: under the IRS rules on home mortgage interest in Publication 936, interest is deductible only when the borrowed money is used to buy, build or substantially improve the home securing the loan.

If the purpose is a single known expense at a known time, such as a roof or a debt consolidation with a fixed total, the 10-year fixed second mortgage is the simpler instrument to budget. If the need is staged spending over months, the HELOC's flexibility can be worth the rate risk. Price the fixed option here, then ask any HELOC lender for the fully indexed rate and the repayment-period payment before comparing.