Home Equity Line of Credit Calculator and Payment Estimate

A home equity line of credit (HELOC) calculator estimates interest-only payments on the amount you draw, using your balance and annual interest rate. Enter the amount borrowed, APR, and repayment period to see an illustrative monthly payment and total interest; actual HELOC payments depend on the lender’s terms and whether the line is in its draw or repayment period.

Formula

This calculator uses the standard level-payment loan formula. It treats the amount drawn as a fully amortizing balance, with equal monthly payments over the stated repayment period:

Monthly payment = P × r ÷ [1 − (1 + r)⁻ⁿ]

• P is the amount drawn, in dollars.
• r is the monthly interest rate, calculated as APR ÷ 1,200. APR is entered as a percentage per year.
• n is the number of monthly payments, calculated as years × 12.

Estimated total interest is the monthly payment multiplied by the number of payments, minus the original balance: total interest = monthly payment × n − P. The result uses the payment rounded to cents, so the total is an estimate based on repeated equal payments.

Worked Example

Using the calculator’s defaults—$20,000 drawn, 8% APR, and a five-year repayment period:

1. Convert APR to a monthly rate: 8 ÷ 1,200 = 0.0066667, or about 0.66667% per month.
2. Convert the period to payments: 5 × 12 = 60 months.
3. Apply the payment formula: $20,000 × 0.0066667 ÷ [1 − (1.0066667)⁻⁶⁰] = about $405.53 per month.
4. Estimate total interest using the rounded monthly payment: $405.53 × 60 − $20,000 = $4,331.80.

The estimated monthly payment is $405.53, and estimated total interest is $4,331.80.

Assumptions

• The APR stays fixed throughout the modeled repayment period.
• Payments are made monthly at the end of each period, with the first payment one month after repayment begins.
• Interest compounds monthly at APR ÷ 12.
• The calculation assumes the full balance is being repaid with equal principal-and-interest payments. It does not include fees, taxes, insurance, or escrow.
• It does not model new draws, minimum-payment rules, a changing rate, or a separate draw period.

How a HELOC Works and What the Estimate Means

A HELOC is a revolving credit line secured by a borrower’s home. The lender sets a credit limit, and the borrower may draw funds up to that limit under the account’s terms. Interest is generally charged on the outstanding amount, rather than on the entire unused limit. A HELOC is therefore not necessarily the same as a one-time lump-sum home equity loan.

Many HELOCs have a draw period followed by a repayment period. During the draw period, borrowing may be available and payments may be calculated differently from the later repayment phase. When repayment starts, new draws may stop and the required payment can rise as the outstanding balance is paid down. The duration and payment rules vary by contract; check the lender’s disclosure for the actual schedule.

This calculator simplifies the repayment phase: it assumes you already owe the entered amount and repay it in equal monthly installments at an unchanged APR. It does not estimate how much a lender may let someone borrow, since that depends on lender-specific information and terms not included here.

When to Use It and How to Read the Results

Use the estimate to understand how a stated balance, APR, and repayment timeline translate into a modeled monthly payment and interest total. For instance, the default example says that paying off $20,000 over 60 months at an assumed fixed 8% APR would require about $405.53 monthly under this formula. It is not a quote or a prediction of a specific HELOC bill.

• Enter the amount you expect to owe, not the total credit limit unless you expect to draw all of it.
• Use the APR supplied for the period you want to examine. If the rate is variable, test more than one rate as separate scenarios rather than treating one result as certain.
• Enter the repayment period in years. A shorter period generally raises the calculated monthly payment and reduces the number of months over which interest accrues, all else equal.
• Compare the result with the payment method in the lender’s documents. A minimum payment, interest-only payment, or variable-rate payment can differ substantially from a fully amortizing installment.

All monetary values are estimates in dollars. The formula rounds the displayed monthly payment to the nearest cent; actual statements can differ because of payment dates, daily interest calculations, rate changes, rounding practices, fees, or contract-specific rules.

Common Limits and Mistakes

The most important limitation is that a HELOC may have a variable APR, while this calculator holds the rate constant. If the rate changes, the interest portion and required payment may change too. The calculation also assumes a level monthly payment that fully pays the balance by the end of the selected period. It cannot represent a payment that covers only interest, a changing balance from additional draws, or a balloon payment unless those terms happen to match the modeled schedule.

• Confusing the credit limit with the balance: interest and payments are modeled on the amount drawn.
• Entering the wrong rate format: enter 8 for 8%, not 0.08. The formula converts the annual percentage into a monthly decimal rate.
• Ignoring rate changes: an estimate at today’s APR does not show what future variable rates may be.
• Assuming the output is a required payment: the contract’s payment provisions control the actual bill.
• Overlooking charges: fees and other costs are excluded, so the interest total is not an all-in borrowing cost.

For an accurate account-specific estimate, review the current balance, APR, payment rules, and any applicable charges in the lender’s documents. A lender may also provide an amortization schedule that reflects the contract’s exact calculation method.

Frequently Asked Questions

How do I calculate a HELOC payment?
For a fixed rate and equal monthly payments, use the amortizing payment formula shown above with the amount drawn, monthly rate, and number of payments. A HELOC’s actual payment may use a different method.

Is a HELOC payment usually interest-only?
Payment rules depend on the contract and the phase of the line. Some arrangements may calculate payments differently during a draw period than during repayment, so check the lender’s disclosures rather than assuming this calculator’s payment applies.

Does the calculator include the unused credit limit?
No. It models interest and repayment on the balance entered. An unused portion of a credit line is not treated as money borrowed here.

What happens if my HELOC rate changes?
A changed APR changes the interest calculation and can affect the required payment. This calculator assumes one fixed APR, so rerun it with another rate to see a separate hypothetical scenario; it cannot predict future rates.

Why is my actual payment different from the estimate?
The calculator assumes a fixed rate and equal monthly amortizing payments. Your account may have a variable rate, a different payment rule, additional draws, fees, or a different interest calculation and payment schedule.

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

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in bal | Amount drawn | $ | 20000 | 1 | 100000000
in apr | Interest rate (APR) | % | 8 | 0.01 | 100
in yrs | Repayment period | years | 5 | 0.0833 | 50
out pmt | Monthly payment | $ | bal * (apr / 1200) / (1 - (1 + apr / 1200) ^ -(yrs * 12)) | 2
out int | Total interest | $ | pmt * yrs * 12 - bal | 2