Home Equity Line of Credit Definition and Calculator

A home equity line of credit (HELOC) is a revolving loan secured by your home: a lender approves a credit limit, and you borrow from it as needed, generally paying interest on the amount used. This calculator estimates a fixed-rate monthly payment and total interest for a fully drawn HELOC balance; enter the balance, annual percentage rate (APR), and repayment term to see both results.

Formula

The calculator uses the standard fixed-payment amortization formula. It treats the entered HELOC balance as a loan repaid in equal monthly payments over the entered term:

• Monthly rate r = APR / 1200, where APR is expressed as a percentage per year.
• Number of payments n = repayment term in years × 12 months per year.
• Monthly payment = round[balance × r / (1 − (1 + r)⁻ⁿ), 2].
• Total interest = rounded monthly payment × n − starting balance.

Here, the HELOC balance p and payment are in dollars, the APR is a percentage, the monthly rate r is a decimal, and n is the number of monthly payments. The payment is rounded to the nearest cent before total interest is calculated, so the total follows the displayed payment.

Worked Example

Using the defaults—$20,000 borrowed, 8% APR, and a five-year repayment term:

1. Convert the APR to a monthly rate: 8 / 1200 = 0.0066667.
2. Convert the term to monthly payments: 5 × 12 = 60.
3. Apply the payment formula: $20,000 × 0.0066667 / [1 − (1.0066667)⁻⁶⁰] = approximately $405.53 per month after rounding.
4. Calculate interest using the rounded payment: $405.53 × 60 − $20,000 = $4,331.80.

The estimate is therefore a monthly payment of $405.53 and total interest of $4,331.80, assuming the balance, APR, and payment schedule remain as entered.

Assumptions

• The APR remains fixed for the full modeled repayment term.
• Payments are equal, made monthly, with the first payment one month after repayment begins.
• Interest compounds monthly at APR / 12.
• The estimate excludes lender fees, taxes, insurance, property costs, and any other charges; none are calculator inputs.
• The balance is treated as fully borrowed at the start of repayment. The calculation does not model additional withdrawals or a separate draw period.

How a HELOC Works

A HELOC is a revolving credit line secured by the borrower’s home. “Revolving” means that, within the approved limit and applicable account terms, the borrower can draw funds, repay some or all of what was borrowed, and potentially borrow again. It is different from receiving one lump sum at the start, as with a typical home equity loan.

The lender sets a credit limit after evaluating the application and the property. The available amount is not the same as home equity itself: equity is the home’s value minus debts secured against it, while the amount a lender may make available depends on its own assessment and terms. Approval, limits, pricing, and fees are lender-specific; get the actual figures and conditions from the lender’s disclosures.

Many HELOCs separate the account into a draw period and a repayment period. During the draw period, withdrawals may be allowed, and required payments can be structured differently from payments later. When repayment begins, access to further borrowing may end and the required payment can change, particularly if the balance must then be repaid over a defined period. The account agreement determines the schedule. The calculator above models only a simplified, fully drawn balance being repaid with equal payments.

What the Calculator Does—and Does Not—Show

This is a comparison of loan arithmetic under stated assumptions, not a prediction of a particular HELOC bill. Actual HELOCs can have variable APRs, changing balances, minimum-payment rules, fees, and terms that do not match a standard installment loan. If the rate changes or you take more draws, your payment and total interest can differ from the estimate.

For example, entering $20,000 assumes that the full amount is already borrowed. If you instead draw $5,000 now and another $5,000 several months later, interest accrues on different balances over different periods. A single starting balance cannot represent that pattern accurately. Likewise, if the contract requires interest-only payments during a draw period, this calculator’s principal-and-interest payment formula does not reproduce those payments.

Use the result to understand how balance, rate, and repayment length affect a simplified payment estimate. For account-specific payment amounts, changing-rate scenarios, fees, and withdrawal rules, use the lender’s disclosures and payment schedule.

HELOC Compared With a Home Equity Loan

Both products use a home as collateral, but their borrowing structures differ. A home equity loan generally provides a lump sum with a repayment schedule for that amount. A HELOC provides access to a credit line that can be drawn over time, subject to the account’s rules. A HELOC balance and required payment can therefore vary with withdrawals, repayments, and rate changes; a fixed-rate installment loan is more straightforward to estimate with the formula here.

Neither label alone tells you the full cost or risk. Review the APR structure, payment requirements, fees, draw and repayment periods, and what happens if a payment is missed. Because a HELOC is secured by the home, failing to meet the contract’s obligations can put the property at risk. Understand the agreement and seek qualified assistance if any term is unclear.

Common Questions and Misconceptions

A common misconception is that a credit limit is money already borrowed. It is not: interest is generally calculated on the amount outstanding, according to the account terms, rather than on all unused credit. Another is that a HELOC always has an interest-only draw-period payment or a variable rate. Those features depend on the contract and should not be assumed without checking the disclosures.

Also distinguish an estimated payment from an approved payment. This tool does not evaluate eligibility, determine an available credit line, or establish what a lender will charge. Its inputs are examples or figures the reader supplies; use the actual terms presented for a specific account when making calculations.

Frequently Asked Questions

What does HELOC stand for?
HELOC stands for home equity line of credit. It is revolving credit secured by a home, with borrowing and repayment governed by the account agreement.

Is a HELOC the same as a home equity loan?
No. A home equity loan generally pays a lump sum, while a HELOC provides a credit line that may be drawn over time. Their payment structures and terms can differ.

Do you pay interest on the full HELOC limit?
Generally, interest is tied to the outstanding amount borrowed, not unused credit, but the contract controls how charges are calculated. Check the lender’s disclosures for the specific account.

Can a HELOC payment change?
Yes. Payments may change when the balance, interest rate, or repayment phase changes, depending on the contract. A variable rate or new repayment schedule can make the actual payment differ from this fixed-rate estimate.

Does a HELOC put your home at risk?
Yes. A HELOC is secured by the home, so failing to meet the agreement’s obligations can put the property at risk. Review the terms and payment requirements before borrowing.

This result is an estimate; the lender’s disclosure gives the exact figures.

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in p | HELOC balance | $ | 20000 | 1 | 100000000
in apr | Interest rate (APR) | % | 8 | 0.01 | 100
in yrs | Repayment term | years | 5 | 0.0833 | 50
out pmt | Monthly payment | $ | round(p * (apr / 1200) / (1 - (1 + apr / 1200) ^ -(yrs * 12)), 2) | 2
out int | Total interest | $ | pmt * yrs * 12 - p | 2