HELOC Cost Calculator: Estimate Monthly Payments

This HELOC calculator estimates a monthly payment and total interest for a fixed-rate draw on a home equity line of credit, using the amount borrowed, APR, and repayment term you enter. The estimate assumes equal monthly payments that repay both principal and interest; it does not model a variable-rate draw period or lender-specific fees.

Formula

The calculator uses the standard fixed-payment loan formula. It converts the annual percentage rate (APR) to a monthly rate, calculates the payment needed to amortize the amount borrowed over the selected number of months, rounds that payment to cents, and estimates total interest from the rounded payment.

Monthly payment: M = round[P × r ÷ (1 − (1 + r)⁻ⁿ), 2]

Total interest: I = (M × n) − P

• P is the amount borrowed, in dollars.
• APR is the annual percentage rate entered as a percentage.
• r is the monthly rate, calculated as APR ÷ 1,200.
• n is the number of monthly payments, calculated as years × 12.
• M is the monthly payment, in dollars, rounded to the nearest cent.
• I is estimated total interest, in dollars.

For example, an APR of 8% becomes a monthly rate of 0.0066667. This calculation treats the rate as fixed and assumes the same payment is made once each month. It is an estimate of repayment arithmetic, not a quote for a particular home equity line.

Worked Example

Using the calculator’s default inputs—$20,000 borrowed, 8% APR, and five years—the number of payments is 5 × 12 = 60, and the monthly rate is 8 ÷ 1,200 = 0.0066667.

1. Substitute into the payment formula: M = 20,000 × 0.0066667 ÷ [1 − (1 + 0.0066667)⁻⁶⁰].
2. The unrounded payment is approximately $405.53; rounded to the nearest cent, the monthly payment is $405.53.
3. Multiply the rounded payment by the 60 payments: $405.53 × 60 = $24,331.80 in total scheduled payments.
4. Subtract the amount borrowed: $24,331.80 − $20,000 = $4,331.80 in estimated total interest.

Because the payment is rounded before the interest total is calculated, small differences from a lender’s final schedule can arise. Lenders may use different payment timing, rate adjustments, or rounding conventions.

Assumptions

• The APR stays fixed for the entire repayment term.
• Payments are equal, made monthly, and include principal and interest.
• Interest compounds monthly at APR ÷ 12.
• Fees, taxes, insurance, and escrow are not included; the calculator has no inputs for them.
• The calculation assumes the full entered amount is borrowed and repaid over the entered term, with no additional draws or extra payments.

What a HELOC Costs

A home equity line of credit (HELOC) is a revolving credit line secured by a borrower’s home. Unlike a one-time lump-sum loan, it generally allows borrowing and repayment within the line’s terms. The amount drawn, rate, payment structure, and timing all affect what the borrower pays. “How much for a HELOC?” can therefore mean the payment on a balance, the interest charged, or the fees and other costs associated with opening and using the line.

This calculator answers a narrower question: what would monthly principal-and-interest payments look like if a specified balance were repaid at a specified fixed APR over a specified term? Enter the amount actually borrowed, rather than the credit limit. A $50,000 approved line with only $20,000 drawn is not the same as borrowing $50,000; interest calculations ordinarily concern the outstanding balance, though product terms and fees can differ.

Why Actual HELOC Payments Can Differ

Many HELOCs have distinct borrowing and repayment periods. During a draw period, the borrower may be able to take additional advances, and payments may be calculated differently from the fully amortizing payments shown here. When that period ends, repayment terms can change, and a balance may need to be repaid over a defined schedule. The specific agreement determines the details.

HELOC rates may also be variable. If the rate changes, the interest charged and required payment can change as well. This calculator does not forecast rate changes or reproduce a lender’s draw-period rules. For a realistic comparison with a particular offer, obtain the lender’s disclosed rate, payment schedule, fee list, and information about how payments are recalculated. Entering a variable product’s current APR as though it were fixed is only a what-if illustration, not a prediction of future cost.

Other potential charges can include application, appraisal, annual, transaction, or early-termination fees, depending on the lender and agreement. Do not assume every HELOC has each charge—or that the calculator includes them. Request a written, itemized explanation of applicable charges and ask whether they are paid upfront, added to the balance, or charged later.

How to Use the Estimate

• Enter the balance you want to evaluate, not automatically the maximum available line.
• Use the APR and term supplied for the specific scenario you are modelling. Rates and fees are inputs, not universal figures; obtain actual terms from the lender.
• Read the monthly payment as the level principal-and-interest payment under the calculator’s fixed-rate assumption.
• Read total interest as an estimate across all modeled payments. It excludes fees and assumes no extra draws, missed payments, or early payoff.
• Change one input at a time to see how a different balance, APR, or repayment length affects the arithmetic.

A longer repayment term generally spreads repayment across more months and can reduce the calculated payment, while interest accrues for longer. A shorter term generally means fewer payments but a larger monthly amount. These are mathematical effects under the stated assumptions, not a recommendation about which term to select. Compare the payment schedule and total costs in the lender’s documents before relying on a figure.

HELOC Cost Compared With Other Borrowing

A HELOC is secured by home equity, while a personal loan or credit card is generally structured differently. A home equity loan usually provides a lump sum with scheduled payments; a HELOC provides access to a line that can be drawn over time subject to its terms. Comparing products requires more than comparing a displayed APR: consider whether the rate can change, when principal repayment begins, how much is drawn, what fees apply, and whether the payment estimate covers principal as well as interest.

One common misconception is that a HELOC’s advertised or initial payment necessarily represents the payment throughout the life of the balance. It may not, especially if the line has a draw period or variable rate. Another is that the credit limit is the same as the amount borrowed. Interest and repayment depend on the outstanding balance and contract terms, not merely the headline limit. Since the home secures a HELOC, missed payments can have serious consequences; the calculator cannot assess that risk or determine eligibility.

Frequently Asked Questions

How much is a HELOC payment on $20,000?
It depends on the APR, repayment period, payment rules, and fees. With this calculator’s defaults—8% fixed APR and five years—the estimated monthly principal-and-interest payment is $405.53. That example is not a lender quote.

Does a HELOC calculator include fees?
No. This calculator estimates payment and interest from the entered balance, APR, and term. Ask the lender for an itemized fee schedule and check whether charges are paid separately or added to the balance.

Are HELOC payments always fixed?
No. A HELOC may have a variable rate, and payments can depend on whether the account is in a draw or repayment period. This calculator assumes a fixed APR and equal monthly payments.

Is the HELOC limit the amount used to calculate interest?
Not necessarily. The limit is the maximum credit available under the agreement; the amount drawn is the balance borrowed. This estimate uses the amount entered as already borrowed.

Can I use this to predict future payments on a variable-rate HELOC?
No. It can show a hypothetical payment at one APR, but it cannot predict future rate changes or lender recalculations. Use the lender’s current disclosures for the product’s actual payment terms.

This result is an estimate, and 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 | Monthly payment | $ | round(p * (apr / 1200) / (1 - (1 + apr / 1200) ^ -(yrs * 12)), 2) | 2
out int | Total interest | $ | pmt * yrs * 12 - p | 2