HELOC Calculator: Estimate Payments and Interest

A home equity line of credit (HELOC) calculator estimates a payment and total interest for a simplified, fully drawn balance repaid in equal monthly installments. Enter the amount borrowed, APR, and repayment term to see the estimated monthly payment and interest; a real HELOC may have changing balances, rates, and payment rules that this model does not capture.

Formula

This calculator treats the HELOC balance as a fixed-rate installment loan after the full amount has been borrowed. It uses the standard level-payment formula, with monthly interest and a payment rounded to cents:

Monthly payment = P × r ÷ [1 − (1 + r)⁻ⁿ], rounded to the nearest cent.

Total interest = (rounded monthly payment × number of monthly payments) − amount borrowed.

• P is the amount borrowed, in dollars.
• APR is the annual percentage rate entered as a percent, such as 8 for 8%.
• r is the monthly rate, calculated as APR ÷ 1,200.
• n is the number of monthly payments, calculated as repayment years × 12.

The formula assumes the entire balance is outstanding from the start of repayment. It does not calculate a draw schedule or changing balance.

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 ÷ 1,200 = 0.0066667, or about 0.66667% per month.
2. Convert the term to payments: 5 × 12 = 60 monthly payments.
3. Apply the payment formula: $20,000 × 0.0066667 ÷ [1 − (1 + 0.0066667)⁻⁶⁰] = approximately $405.53 per month, rounded to cents.
4. Calculate total interest using the rounded payment: ($405.53 × 60) − $20,000 = $4,331.80.

The calculator therefore returns an estimated monthly payment of $405.53 and estimated total interest of $4,331.80.

Assumptions

• The APR stays fixed for the entire repayment term.
• 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 full amount is borrowed at the beginning and repaid in equal payments.
• Fees, taxes, insurance, and other charges are not included.

What a HELOC Is and How It Works

A HELOC is a revolving credit line secured by a home. Rather than receiving one lump sum, a borrower may draw funds as needed up to the credit limit, subject to the account’s terms. The home is collateral, so failure to meet repayment obligations can put the property at risk.

Many HELOCs have a draw period followed by a repayment period. During the draw period, the borrower may be able to borrow, repay, and borrow again; required payments may be based on the outstanding balance and contract terms. When the draw period ends, new borrowing may stop and repayment of the remaining balance begins. Some plans require principal payments during the draw period, while others may permit interest-only payments for a time. The agreement controls the actual schedule.

Because the balance can change as money is drawn or repaid, a single fixed-payment estimate is not a complete projection of a typical HELOC. It is most useful as a comparison point for a hypothetical balance repaid over a selected term.

How to Use the Estimate

• Amount borrowed: Enter the balance you want to model, not automatically the full credit limit. If you expect to draw in stages, the calculator’s immediate full-balance assumption will differ from that pattern.
• APR: Enter the rate applicable to the balance and period you are examining. Check whether the lender’s quoted figure is variable, and how its terms describe rate changes.
• Repayment term: Use the number of years over which you want to model equal payments. This is a calculation input, not a statement about a specific account’s required term.

Use the payment result to understand the effect of these inputs, then compare the assumptions with the account’s actual disclosures. The total-interest result is the modeled interest over all payments, not the total cost of borrowing if fees or other charges apply.

HELOC Costs, Risks, and Common Misunderstandings

A quoted credit limit is not the same as an amount borrowed: interest calculations generally depend on the outstanding balance and the agreement’s rules. Drawing more money can increase the balance and the amount of interest due. Conversely, repaying principal can reduce the amount outstanding, although details depend on the account.

Some HELOCs have variable rates. If the rate changes, the payment, payoff time, or total interest may differ from this fixed-rate illustration. Review the contract for how the rate is determined, when it can change, any applicable limits, fees, payment requirements, and what happens at the end of the draw period. Do not assume an interest-only payment will repay principal.

A further misconception is that a HELOC is simply a second mortgage with a fixed lump-sum payment. Both involve borrowing secured by a home, but a HELOC’s revolving access and possible rate changes make its balance and payments less predictable. The lender’s disclosures and agreement, rather than this calculator, define the account’s terms.

HELOCs Compared With Other Borrowing Options

A home equity loan commonly provides a lump sum with a scheduled repayment structure, while a HELOC provides access to a revolving line under its terms. A personal loan is generally not secured by the borrower’s home, though it has its own eligibility, rate, and repayment conditions. These products differ in collateral, access to funds, rate structure, fees, and payment timing. The calculator does not compare product pricing or determine which option fits a particular situation.

For any borrowing option, compare the amount received, APR and whether it can change, fees, required payments, repayment period, and consequences of missed payments. Get exact figures and terms directly from the relevant provider; this page does not model lender-specific terms or approval.

Frequently Asked Questions

Is a HELOC payment usually fixed?
A HELOC payment depends on its contract. A variable rate, changing balance, draw-period rules, or transition to repayment can change the amount due. This calculator assumes a fixed APR and equal monthly payments.

Does this calculator include the draw period?
No. It assumes the full modeled balance is borrowed at the start of repayment. It does not calculate draws over time, payments during a draw period, or a later transition between phases.

Why might my lender’s payment differ from this estimate?
The account may use a different balance, rate, payment schedule, compounding or rounding method, or include fees. A variable APR or staged withdrawals can also change the result. Check the lender’s payment disclosures.

Can a HELOC rate change?
Some HELOCs have variable rates and some terms may provide for changes. Whether and how a rate changes depends on the agreement; review its rate provisions rather than assuming the APR remains constant.

Does a HELOC put my home at risk?
A HELOC is secured by the home. Not meeting the account’s repayment obligations can have serious consequences for the property. Read the agreement and contact the provider if you need clarification about obligations or payment difficulties.

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

Related

• Bank Home Equity Line of Credit Calculator
• Aven Home Equity Line of Credit: How It Works
• Apply for a Home Equity Line of Credit Online?

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 | $ | p * (apr / 1200) / (1 - (1 + apr / 1200) ^ -(yrs * 12)) | 2
out int | Estimated total interest | $ | pmt * yrs * 12 - p | 2