2nd Mortgage Calculator

Reviewer: David Chen, CFA. Last updated: December 2025.

Use this comprehensive 2nd Mortgage Calculator to estimate your monthly payments, helping you budget for a Home Equity Loan (HEL) or Home Equity Line of Credit (HELOC) and understand your total borrowing costs.

2nd Mortgage Payment Calculator

Estimated Monthly Payment:

$0.00

Detailed Calculation Steps:

2nd Mortgage Calculator Formula

This calculator uses the standard fixed-rate amortization formula to determine your scheduled monthly payment. The formula assumes a fixed principal and interest loan, such as a Home Equity Loan (HEL).

$$M = P \frac{i(1+i)^n}{(1+i)^n – 1}$$

Formula Source: Investopedia: Amortization, Bankrate: Payment Calculation

Variables Used in the Calculation:

  • M (Monthly Payment): The total amount paid each month. This is the result the calculator solves for.
  • P (Principal Loan Amount): The initial amount of money borrowed for the 2nd mortgage.
  • i (Monthly Interest Rate): The Annual Interest Rate (R) divided by 12 (i = R / 12).
  • n (Total Number of Payments): The Loan Term in Years (T) multiplied by 12 (n = T × 12).

What is a 2nd Mortgage?

A second mortgage is a lien placed against a property that already has an existing mortgage. It is subordinate to the first mortgage, meaning that in the event of default and foreclosure, the first lender is paid off entirely before the second lender receives any funds. This increased risk is why second mortgages typically carry higher interest rates than primary mortgages.

The two most common types of second mortgages are Home Equity Loans (HELs), which provide a lump sum of cash with a fixed interest rate and fixed payment schedule, and Home Equity Lines of Credit (HELOCs), which are revolving credit lines that allow the borrower to draw funds as needed, typically with variable interest rates.

Using a calculator to estimate monthly payments is crucial before taking out a second mortgage, as it ensures the new debt fits comfortably within your household budget, taking into account the higher cost of borrowing.

How to Calculate 2nd Mortgage Payments (Example)

Let’s calculate the monthly payment for a $40,000 second mortgage over 10 years at an 8.0% annual interest rate:

  1. Identify Variables: P = $40,000, R = 8.0%, T = 10 years.
  2. Calculate Monthly Rate (i): $i = 0.08 / 12 \approx 0.006667$.
  3. Calculate Total Payments (n): $n = 10 \times 12 = 120$ payments.
  4. Plug into Formula: $$M = 40,000 \times \frac{0.006667(1+0.006667)^{120}}{(1+0.006667)^{120} – 1}$$
  5. Solve: The resulting monthly payment, M, would be approximately $485.26.

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Frequently Asked Questions (FAQ)

What is the maximum Loan-to-Value (LTV) ratio for a 2nd mortgage?
Typically, lenders allow combined LTVs (CLTV) up to 80% or 85% of your home’s value, though some programs may go higher for highly qualified borrowers. This limit is set to protect the lender from losses.

Are 2nd mortgage payments tax-deductible?
Interest on a second mortgage may be tax-deductible if the funds are used to buy, build, or substantially improve the home that secures the loan. Consult a tax professional for personalized advice.

Is a Home Equity Loan (HEL) better than a HELOC?
A HEL is better if you need a specific, fixed amount of cash and prefer a fixed interest rate and predictable monthly payments. A HELOC is better if you need flexible access to funds over time and don’t mind a variable interest rate.

What closing costs are associated with a second mortgage?
Closing costs are usually lower than a first mortgage but can include application fees, appraisal costs, title search fees, and origination fees. They typically range from 2% to 5% of the loan amount.

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