Home Equity Line of Credit: How It Works

A home equity line of credit (HELOC) lets you borrow against available equity in your home, up to a lender-approved limit, and draw money as needed during a set period. This calculator estimates a fully amortizing monthly payment and total interest if you borrow one amount, at a fixed APR, and repay it over the entered term; enter the amount, rate, and years to see the estimates.

Formula

The calculator treats the entered draw as a fixed-rate installment loan with equal monthly payments. It does not model a revolving HELOC balance, changing rates, or a draw period.

• Monthly rate, r: APR ÷ 1,200, expressed as a decimal rate per month.
• Number of payments, n: repayment term in years × 12 months per year.
• Monthly payment: round to cents: P × r ÷ [1 − (1 + r)⁻ⁿ].
• Total interest: monthly payment × n − P.

P is the amount borrowed in dollars; APR is the entered annual percentage rate; r is the monthly rate; and n is the number of monthly payments. The interest total uses the rounded monthly payment, so it can differ slightly from a calculation using an unrounded payment.

Worked Example

Using the calculator’s defaults—$20,000 borrowed, 8% APR, and five years—there are 5 × 12 = 60 monthly payments. The monthly rate is 8 ÷ 1,200 = 0.0066667.

Monthly payment = round[20,000 × 0.0066667 ÷ (1 − (1.0066667)⁻⁶⁰), 2] = $405.53.

Total interest = $405.53 × 60 − $20,000 = $4,331.80. These figures are an illustration of the formula, not a quote for a HELOC.

Assumptions

• The APR and payment remain fixed throughout repayment.
• Payments are made monthly, with the first payment one month after borrowing.
• Interest compounds monthly at APR ÷ 12.
• Fees, taxes, insurance, required minimums, and any draw-period payments are not included.

How a HELOC Works

A HELOC is secured by your home. Equity is broadly the home’s value minus debts secured by it, but a lender determines how much credit may be available after evaluating the property and application. The approved credit limit is not necessarily the amount you borrow: interest generally applies to the balance drawn, according to the agreement.

Most HELOC agreements divide the timeline into a draw period and a repayment period. During the draw period, you can borrow, repay, and potentially borrow again up to the available limit, subject to the contract. When that period ends, further draws usually stop and repayment begins. The balance may then be paid over time, and payments can rise if the repayment schedule is shorter or the rate changes.

For example, if a line has a $40,000 limit and you draw $12,000, the unused portion is not automatically a debt. If you later repay $2,000, the amount available to draw may increase by that amount, subject to the line’s terms. The calculator instead assumes a single $20,000 draw and immediate repayment over five years; it cannot forecast interest on repeated draws or payments during an actual draw period.

Rates, Payments, and Costs

Many HELOCs have a variable interest rate, though contract structures differ. A rate change can affect the interest charged and may change the required payment. Some agreements may allow a fixed-rate option for part of the balance, but availability and terms must be checked in the lender’s disclosure. Enter the rate that applies to the amount and period you want to estimate; the calculator’s fixed-rate assumption will not capture future adjustments.

Also review charges and payment rules rather than comparing only the advertised credit limit or initial payment. Depending on the agreement, costs may include application, appraisal, account, transaction, or early-closure charges. Check whether a minimum payment covers principal as well as interest, how payments are calculated, and whether a final payment could be larger than earlier payments. Get the actual figures and terms from the lender.

HELOC Compared With Other Borrowing

A HELOC differs from a home equity loan, which generally provides a lump sum repaid under a fixed schedule. A HELOC is revolving during its draw period, so the balance can change as you borrow and repay. A cash-out refinance replaces an existing mortgage with a new mortgage, rather than adding a separate revolving line; costs and effects depend on the specific transaction. Unsecured credit does not use the home as collateral, while a HELOC does. These products have different terms, risks, and costs, so their headline rates alone do not describe the full comparison.

Risks and Practical Checks

Because a HELOC is secured by the home, failing to meet the agreement’s payment obligations can put the home at risk. Borrowing against equity also reduces the portion of the home that is debt-free. Before relying on a line for a project or ongoing expenses, consider whether you could manage payments if rates rise, income changes, or the draw period ends. Do not assume the full credit limit will remain available indefinitely; review the contract’s conditions for access and repayment.

• Confirm the draw-period end date, repayment term, rate-adjustment method, and payment formula.
• Ask how much of each payment goes to principal and whether a balloon or final lump-sum payment is possible.
• Check all fees, balance-conversion options, and rules for reducing or suspending access to credit.
• Keep records of draws and payments, and compare the statement balance with your own tracking.

Frequently Asked Questions

Do you pay interest on the full HELOC limit?
Typically, interest is calculated on the amount borrowed, not simply the unused limit. The agreement governs how balances, fees, and interest are calculated, so verify its terms.

Can a HELOC payment go up?
Yes. Payments can change if a variable rate changes, the repayment period starts, the outstanding balance changes, or the contract uses a different payment calculation. Review the lender’s payment examples and rate provisions.

Is a HELOC the same as a home equity loan?
No. A HELOC is generally a reusable credit line during its draw period; a home equity loan generally provides a lump sum with scheduled repayment. Both may be secured by the home.

What happens when the HELOC draw period ends?
Further borrowing may stop and the balance typically enters repayment under the contract. The required payment may change, so check the schedule and terms before the transition.

Does this calculator show my actual HELOC payment?
No. It estimates payments for one fixed-rate draw repaid in equal monthly installments. It omits revolving draws, variable rates, lender-specific payment rules, and fees. The result is an estimate; the lender’s disclosure gives the exact figures.

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