Home Equity Line of Credit Loan Calculator

A home equity line of credit (HELOC) calculator estimates the monthly payment and total interest on a balance borrowed from a revolving credit line. Enter the amount drawn, APR, and repayment term to see an illustrative fixed-payment estimate; an actual HELOC may have changing rates, draw-period rules, and payment terms that this calculation does not model.

Formula

This calculator treats the amount entered as a single balance repaid through equal monthly payments at a fixed APR. The monthly payment is calculated with the standard amortizing-loan formula:

Payment = P × r ÷ [1 − (1 + r)⁻ⁿ]

• P is the amount borrowed, in dollars.
• r is the monthly interest rate as a decimal: APR ÷ 1200. For an 8% APR, r = 8 ÷ 1200.
• n is the number of monthly payments: term in years × 12.
• Payment is the estimated monthly principal-and-interest payment, in dollars.

Estimated total interest is monthly payment × number of payments − principal. The calculator uses the displayed monthly payment, rounded to cents, in that total. It assumes the same payment each month and does not calculate a minimum payment that changes with the outstanding balance.

Worked Example

Using the calculator’s default inputs—$20,000 borrowed, 8% APR, and five years:

1. Convert APR to a monthly decimal rate: 8 ÷ 1200 = 0.0066667.
2. Find the number of payments: 5 × 12 = 60.
3. Apply the payment formula: $20,000 × 0.0066667 ÷ [1 − (1 + 0.0066667)⁻⁶⁰] = approximately $405.53 per month.
4. Calculate total interest using the rounded payment: $405.53 × 60 − $20,000 = $4,331.80.

The estimate is therefore $405.53 per month, with $4,331.80 in total interest under the stated assumptions. The last payment on a real amortizing loan can differ slightly because of rounding and payment timing.

Assumptions

• The APR remains fixed for the entire repayment term.
• Payments are equal, made monthly, and begin one month after borrowing.
• Interest compounds monthly at APR ÷ 12.
• The estimate excludes fees, taxes, insurance, mortgage insurance, escrow, and any costs associated with opening or maintaining a credit line.
• The full amount entered is borrowed at the outset; later draws and repayments are not modelled.

How a HELOC Differs From This Estimate

A HELOC is generally a revolving line secured by home equity: a borrower may draw funds, repay them, and potentially draw again subject to the line’s terms. That is different from receiving one lump sum and paying it off on a fixed schedule. A HELOC can have a period when borrowing is allowed and a later repayment period; payment calculations and permitted transactions can change between those phases.

Many HELOCs have variable rates, so the interest rate and payment can change over time. This calculator holds APR constant because a single rate is needed for the standard payment formula. It is useful for a what-if estimate at a selected rate, but it cannot predict future rate changes or the resulting payment. Use the APR and repayment details supplied for the particular line, and recalculate scenarios if those inputs change.

Also distinguish the credit limit from the amount borrowed. Interest is generally associated with the outstanding balance, not simply the maximum line shown in an offer, but the lender’s agreement determines the applicable calculation and charges. Enter the balance you want to estimate, not an unused credit limit.

How to Use and Interpret the Results

Enter a principal amount, an APR as a percentage per year, and a repayment term in years. The rate and term must represent the same repayment scenario: for example, do not use a promotional or draw-period rate together with a different repayment-period term unless those figures actually describe the balance you are modelling.

• Change the amount to compare the arithmetic for different hypothetical balances.
• Change APR to see how a different assumed rate affects payment and interest; use a lender-provided figure rather than treating the default as a market quote.
• Change the term to see how the payment schedule affects monthly payment and interest under a fixed rate.

A longer term usually spreads principal repayment across more payments. In this formula, that changes both the monthly payment and the cumulative interest. The output is not an approval decision, a credit limit, or a statement of what a household can afford. It also does not include other housing costs or household expenses.

Common Limits and Mistakes

The most important limitation is treating a revolving, possibly variable-rate HELOC like a fixed-rate installment loan. The result is not a complete forecast when balances change through multiple draws, extra repayments, interest-only payments, rate resets, or a transition from a draw period to repayment. For those cases, calculate separate scenarios for each balance and rate, or use the lender’s payment schedule and disclosures.

• Entering the credit limit instead of the drawn balance: this can overstate the balance being modelled.
• Confusing APR with a monthly rate: enter APR as a yearly percentage, such as 8, not 0.6667. The calculator divides APR by 1200 internally.
• Assuming fees are included: they are not; add them separately only when you know the lender’s figures and how they are charged.
• Reading an estimate as an exact bill: rounding, payment dates, balance changes, and contract terms can produce a different amount due.

The formula also assumes the payment covers both principal and interest throughout the term. It cannot represent payment caps, minimum-payment formulas, or other contract-specific features. APR, fees, and line terms vary; obtain the actual figures and payment rules from the lender’s disclosures.

Frequently Asked Questions

What does a HELOC calculator show?
With the inputs on this page, it estimates the monthly payment and total interest for one balance repaid in equal monthly installments at a fixed APR. It is not a full simulation of a revolving line.

Should I enter my HELOC limit or my balance?
Enter the amount you expect to borrow or the outstanding balance you want to model. A credit limit is the maximum available line, not necessarily the amount drawn.

Can this calculator handle a variable HELOC rate?
No. It assumes one APR for the full term. You can run separate calculations using different assumed rates, but that does not forecast when rates may change or how a lender will adjust payments.

Does a HELOC payment calculator include fees?
No. The outputs cover principal and interest under the formula’s assumptions. Check the lender’s disclosures for fees or other charges that may apply.

Why might my actual payment differ?
A HELOC may use a variable rate, a changing balance, a different payment method, or distinct draw and repayment periods. Payment timing and rounding can also affect the amount due.

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

Related

• Figure Home Equity Line of Credit Calculator
• Five-Year HELOC Payment Calculator and Guide
• Fifth Third Bank HELOC: How Payments Are Calculated

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