Home Equity Line of Credit Calculator and Explanation

A home equity line of credit (HELOC) is a revolving loan secured by your home: you can borrow, repay, and borrow again up to a lender-approved limit during the draw period. This calculator estimates interest-only monthly interest on the amount currently borrowed; enter the balance and annual APR to see an estimated payment and the interest over one year.

Formula

The estimated monthly interest-only payment is the balance multiplied by the annual percentage rate and divided by 12 months: pmt = round(bal × apr / 1200, 2). The calculator expresses APR as a percentage, so dividing by 100 converts it to a decimal and dividing by 12 converts it to a monthly rate. The estimated one-year interest is ann = pmt × 12.

• bal is the current amount borrowed, in dollars.
• apr is the annual percentage rate entered as a percent per year.
• pmt is estimated monthly interest, in dollars, rounded to the nearest cent.
• ann is 12 equal monthly interest payments, in dollars.

This is a simplified interest-only estimate, not a quote or a full HELOC payment schedule. It assumes that the balance and APR stay unchanged throughout the period. It does not calculate principal repayment or a changing-rate payment.

Worked Example

Using the calculator’s default values, the balance is $20,000 and APR is 8%.

1. Convert APR to a monthly decimal rate: 8 ÷ 1,200 = 0.0066667.
2. Multiply the balance by the monthly rate: $20,000 × 0.0066667 = $133.333….
3. Round the monthly amount to cents: $133.33.
4. Multiply the rounded monthly amount by 12: $133.33 × 12 = $1,599.96 in estimated interest over one year.

How a HELOC Works

A HELOC is secured by the home, meaning the property is collateral for the debt. It differs from a conventional installment loan: rather than receiving one fixed lump sum, a borrower may draw funds as needed, subject to the line’s terms and available credit. Repaying principal may restore some available credit during the period when additional draws are permitted.

HELOCs commonly have two stages. During a draw period, the borrower can access the line under the agreement and make required payments. After that, the repayment period begins; new borrowing may no longer be available, and payments can include principal as well as interest. The timing, payment method, duration, and rules vary by contract, so check the lender’s disclosures instead of assuming an interest-only payment will continue.

For example, if someone has borrowed $20,000, this calculator estimates the interest on that balance. It does not determine the full credit limit, how much equity a lender may count, or whether a particular borrower can qualify. Those depend on lender-specific information and assessment.

How to Read the Estimate

The first result is a monthly interest-only amount for the balance and APR entered. It is not necessarily the amount due on a real HELOC statement. A lender may use a different balance calculation, payment convention, rate, or contractual minimum, and a required payment can include principal, fees, or other amounts.

The annual result is simply 12 times the calculator’s rounded monthly estimate. It is useful for understanding the arithmetic under the stated assumptions, not for predicting the total cost of borrowing over a HELOC’s lifetime. If the balance changes, or the rate changes, the interest estimate changes too.

Rates, Costs, and Common Misunderstandings

Some HELOCs have variable rates, while the exact rate structure and adjustment terms depend on the agreement. If the APR rises, the interest calculated on an unchanged balance rises; if the balance falls, interest generally falls when the rate and calculation method stay the same. A displayed APR should not be treated as a guaranteed future rate unless the contract says so.

The calculator includes no fees, closing costs, annual charges, payment penalties, or other contract-specific costs. It also does not estimate taxes or determine whether interest qualifies for any tax treatment. For actual figures, consult the lender’s current disclosures and, for tax questions, an appropriately qualified tax professional.

• Interest is not principal repayment. Paying the estimated interest alone would not reduce the $20,000 balance.
• The line limit is not the borrowed balance. Interest is calculated on amounts borrowed, not automatically on all available credit.
• APR is not a monthly rate. The formula divides a percent APR by 1,200 to get a monthly decimal rate.
• Variable rates can change. A single entered APR cannot represent every future payment when the rate moves.

When This Calculator Helps—and Its Limits

Use the estimate to see how an entered balance and APR translate into simplified monthly interest, or to compare arithmetic scenarios by changing one input at a time. Enter the balance currently borrowed rather than the total credit line. Use the APR supplied for the scenario you want to examine; the example default is only an input for demonstrating the formula, not a statement about available rates.

This tool does not calculate an amortizing payment, a payoff date, borrowing capacity, or approval. It cannot model draw-period rules, daily balance methods, rate floors or caps, payment changes, or future draws. Those details require the actual agreement and, where applicable, the lender’s payment schedule.

Frequently Asked Questions

Is a HELOC the same as a home equity loan?
A HELOC is generally a revolving line that can be drawn in stages under its terms. A home equity loan generally provides a lump sum repaid according to an installment schedule. Both can be secured by a home, but their structures differ.

Does a HELOC payment reduce the amount I owe?
It depends on the payment requirement and stage of the line. An interest-only payment covers interest but does not reduce principal; a payment that includes principal reduces the balance by the amount applied to it.

Can the interest rate on a HELOC change?
It can if the agreement has a variable-rate structure. Review the contract for how the rate is set and adjusted; this calculator assumes the entered APR remains unchanged for its estimate.

Is the calculator’s result my actual minimum payment?
No. It is a simplified interest-only estimate. The actual amount due depends on the contract, current balance, rate, payment calculation, and any applicable charges.

What happens when the draw period ends?
The line may enter a repayment stage in which further draws are restricted or unavailable and payments may include principal. The agreement specifies the transition and payment terms.

Assumptions

• APR is fixed at the entered value for the estimate; rate changes are not modelled.
• The calculation assumes monthly interest accrual at APR ÷ 12 and uses an interest-only payment.
• It assumes the same balance for all 12 months and uses the rounded monthly amount for the annual total.
• Fees, taxes, insurance, PMI, escrow, principal repayment, and lender-specific payment rules are not included.

This result is an estimate for education, and the lender’s disclosure gives the exact figures.

Related

• 5-Year Home Equity Line of Credit Rates Explained
• E Loan Meaning, How It Works, and What to Check
• Equity Loan Repayment: Estimate Your Monthly Payment

in bal | Current HELOC balance | $ | 20000 | 0 | 100000000
in apr | Interest rate (APR) | % | 8 | 0.01 | 100
out pmt | Monthly interest-only payment | $ | round(bal * apr / 1200, 2) | 2
out ann | Interest over 12 months | $ | pmt * 12 | 2