How to Calculate Home Equity Loan Payments and Total Interest Cost

What a Home Equity Loan Actually Is

A home equity loan is a fixed-rate, lump-sum second mortgage. You borrow against the difference between your home's current market value and your outstanding mortgage balance. You receive one disbursement. You repay it in equal monthly installments over a set term, typically 5 to 30 years.

This structure differs from a home equity line of credit, which carries a variable rate and revolving balance. Home equity loans carry fixed rates. That predictability is a feature, not a footnote. It means you can calculate the full cost of the loan on day one.

Most borrowers don't do that calculation. They ask the lender what the monthly payment will be and sign. That habit costs real money.

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The Payment Formula

Home equity loan payments use standard amortization. Every monthly payment covers two components: interest on the remaining principal and a reduction of that principal.

The formula is:

M = P × [r(1 + r)^n] / [(1 + r)^n - 1]

Where:

• M = monthly payment
• P = principal loan amount
• r = monthly interest rate (annual rate divided by 12)
• n = total number of payments (years multiplied by 12)

This is the same formula used for any fully amortizing fixed loan. The math does not change because the collateral is your home.

Breaking Down Each Variable

Principal (P). This is the net amount you borrow after any origination fees rolled into the loan. If a lender charges a 1% origination fee on $75,000 and adds it to the balance, your effective principal is $75,750, not $75,000.

Monthly rate (r). A lender quoting 8.5% APR converts to 0.085 divided by 12, which equals 0.007083 per month. This small number compounds across every payment in the schedule.

Number of payments (n). A 10-year term is 120 payments. A 15-year term is 180 payments. The difference of 60 payments is where most of the excess interest hides.

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Worked Example 1: $75,000 at 8.5% Over 15 Years

This scenario reflects a homeowner pulling equity for a major renovation in 2026.

• P = $75,000
• Annual rate = 8.5%
• r = 0.085 / 12 = 0.007083
• n = 15 × 12 = 180

Applying the formula:

M = 75,000 × [0.007083 × (1.007083)^180] / [(1.007083)^180 - 1]

(1.007083)^180 = 3.5004

M = 75,000 × [0.007083 × 3.5004] / [3.5004 - 1] M = 75,000 × [0.024796] / [2.5004] M = 75,000 × 0.009917 M = $743.77 per month

Total paid = $743.77 × 180 = $133,878.60 Total interest = $133,878.60 - $75,000 = $58,878.60

That figure is not a rounding error. You pay back every dollar borrowed, then pay an additional $58,878 for the right to borrow it over 15 years at 8.5%.

How the Same Loan Performs Over 10 Years

Keep the rate at 8.5%, drop the term to 10 years.

• n = 120
• (1.007083)^120 = 2.3589

M = 75,000 × [0.007083 × 2.3589] / [2.3589 - 1] M = 75,000 × [0.016707] / [1.3589] M = 75,000 × 0.012294 M = $922.08 per month

Total paid = $922.08 × 120 = $110,649.60 Total interest = $110,649.60 - $75,000 = $35,649.60

The 10-year term costs $178.31 more per month but saves $23,229 in total interest. That tradeoff requires a deliberate decision, not a default.

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Worked Example 2: $50,000 at 8.0% Over 10 vs. 15 Years

A borrower consolidating high-interest debt often lands in the $40,000 to $60,000 range. This example uses $50,000 at 8.0%.

10-Year Term

• r = 0.08 / 12 = 0.006667
• n = 120
• (1.006667)^120 = 2.2196

M = 50,000 × [0.006667 × 2.2196] / [2.2196 - 1] M = 50,000 × [0.014797] / [1.2196] M = 50,000 × 0.012133 M = $606.64 per month

Total interest = ($606.64 × 120) - $50,000 = $72,796.80 - $50,000 = $22,796.80

15-Year Term

• n = 180
• (1.006667)^180 = 3.3102

M = 50,000 × [0.006667 × 3.3102] / [3.3102 - 1] M = 50,000 × [0.022068] / [2.3102] M = 50,000 × 0.009552 M = $477.83 per month

Total interest = ($477.83 × 180) - $50,000 = $86,009.40 - $50,000 = $36,009.40

The 15-year term saves $128.81 per month. It costs an additional $13,212.60 in total interest. A borrower in a cash-flow-constrained position may accept that cost deliberately. Most borrowers accept it without realizing it.

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How Lender Fees Change the True Cost

The formula above assumes no fees rolled into the principal. Most home equity loans carry closing costs between 2% and 5% of the loan amount. These typically include:

• Origination fees: 0.5% to 1% of the loan
• Appraisal fees: $300 to $600
• Title search and insurance: $200 to $400
• Recording fees: $50 to $150

On a $75,000 loan, a 2% total closing cost adds $1,500. If that amount rolls into the principal, your payment formula runs on $76,500, not $75,000. At 8.5% over 15 years, that $1,500 addition costs an additional $1,178 in interest. The fee compounds.

Always ask the lender for the loan's annual percentage rate, not just the stated interest rate. The APR incorporates fees into the effective cost of borrowing. It is the single most accurate cost comparison number across competing offers.

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The Equity Calculation That Precedes Everything

Before calculating payments, confirm you have sufficient equity to borrow against. Most lenders allow a combined loan-to-value ratio of 80% to 85%.

Usable equity formula:

Available equity = (Home value × 0.80) - Outstanding mortgage balance

If your home is worth $420,000 and your mortgage balance is $280,000:

Available equity = ($420,000 × 0.80) - $280,000 Available equity = $336,000 - $280,000 Available equity = $56,000

At an 85% CLTV cap, that number rises to $77,000. The lender's specific cap determines your ceiling. Request this figure in writing before spending time on payment calculations.

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What Rate to Use When Running Projections

Home equity loan rates in mid-2026 range from approximately 7.8% to 9.6% for borrowers with strong credit profiles. The specific rate you receive depends on:

• Credit score. Borrowers above 760 typically receive rates 0.5% to 1.0% lower than borrowers in the 680 to 720 range.
• CLTV ratio. A 70% CLTV commands a better rate than an 80% CLTV.
• Loan term. Shorter terms often carry marginally lower rates.
• Lender type. Credit unions consistently quote lower rates than national banks on home equity products.

For planning purposes, run three scenarios: your estimated rate, that rate plus 0.5%, and that rate minus 0.5%. The spread in total interest cost across those three scenarios tells you how sensitive your decision is to rate negotiation.

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Comparing Home Equity Loans to Alternatives

A home equity loan is not always the lowest-cost borrowing option. Compare it against:

Cash-out refinance. If current first mortgage rates sit below your existing mortgage rate, a cash-out refinance could lower your blended cost. If your existing rate is below current market rates, a cash-out refinance increases your total mortgage cost even if the rate looks attractive.

HELOC. A home equity line of credit carries variable rates, currently ranging from 8.0% to 10.5% for creditworthy borrowers. If you draw the full amount immediately and rates stay flat, the comparison is direct. If you draw in tranches, the amortization math changes substantially.

Personal loan. Unsecured personal loans carry rates from 10% to 18% for most borrowers. The rate premium over a home equity loan on a $50,000 balance could add $15,000 to $40,000 in total interest. The tradeoff is no collateral risk on your home.

The right product depends on your rate environment, draw schedule, and risk tolerance for variable-rate exposure.

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Run the Numbers Before You Commit

The payment formula gives you a precise monthly obligation. Total interest gives you the true cost of the loan. Both numbers belong in the decision.

Changing a single variable, rate, term, or principal, shifts those numbers materially. A 0.75% rate improvement on a $75,000 loan over 15 years saves $8,347 in total interest. That saving is worth a second lender quote and 45 minutes of your time.

The CalcMoney mortgage calculator runs these figures instantly. Enter your loan amount, rate, and term. Review both the monthly payment and the total interest schedule. Adjust the term and watch how the tradeoff moves. That analysis takes two minutes and eliminates the most common and most expensive mistake borrowers make with home equity loans.

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