HELOC Payment Calculator

Agreement start month:

Use the opening or schedule month stated by the agreement.

Credit limit:

Maximum revolving line before the repayment period.

Opening balance:

Use 0 for an undrawn new line.

Draw period:

months

Months when new draws are allowed.

Repayment period:

months

Months after new draws stop.

Current index:

Public index value from the agreement source.

Contract margin:

points

Percentage points added to the index.

Stress change:

points

Comparison change from index plus margin.

Rate floor:

Lowest effective annual rate in the agreement.

Lifetime rate cap:

Maximum effective annual rate in the agreement.

Draw-period payment rule:

Match the minimum-payment structure in the current agreement.

Monthly draw principal:

Principal paid in addition to monthly interest.

Repayment-period rule:

Amortizing retires the transition balance; fixed payment may leave a balloon.

Fixed repayment payment:

Monthly principal-and-interest payment before fees.

Dated draws and principal repayments:

Optional dated activity updates the revolving balance path. {{ events.length }} of 24 rows used.

Month	Type	Label	Amount	Remove

No dated events. The schedule starts from the opening balance.

Upfront fees:

Neutral default: $0. Cash costs in the first modeled month.

Annual fee:

Neutral default: $0. Applied after each modeled 12-month interval.

Fee per draw:

Neutral default: $0. Applied once for each dated draw.

Payment outlook

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How this estimate is built:

monthly interest = balance × effective annual rate ÷ 12

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Planning estimate only. Compare the monthly convention, payment rule, fees, floor, and cap with the current lender agreement; missed payments can put the home at risk.

The chart renderer is unavailable. The same scenario values remain in Payment outlook and the CSV export.

Monthly HELOC draw and repayment ledger in US dollars
Month	Phase	APR	Events	Opening balance	Draws	Extra principal	Interest	Scheduled principal	Fees	Cash payment	Ending balance	Available credit	Copy
{{ formatMonth(row.month) }}	{{ row.phase }}	{{ row.effective_apr }}	{{ row.events }}	{{ formatCurrency(row.opening_balance) }}	{{ formatCurrency(row.draws) }}	{{ formatCurrency(row.extra_principal) }}	{{ formatCurrency(row.interest) }}	{{ formatCurrency(row.scheduled_principal) }}	{{ formatCurrency(row.fees) }}	{{ formatCurrency(row.cash_payment) }}	{{ formatCurrency(row.ending_balance) }}	{{ formatCurrency(row.available_credit) }}

A home equity line of credit (HELOC) is revolving debt secured by a home. During the draw period, the borrower can usually take additional advances up to the available limit and may face a relatively low minimum payment. When that period ends, new draws stop and repayment terms can raise the monthly payment sharply.

Most HELOCs have variable rates. The contract normally names a public index and adds a fixed margin, then applies any floor, periodic limit, or lifetime cap written into the agreement. A payment estimate is only as current as the index value entered, and a stress-rate scenario is a planning comparison rather than a forecast.

Typical differences between HELOC draw and repayment periods
Phase	New borrowing	Common payment pattern	Main planning risk
Draw period	Allowed within the credit limit	Interest only or interest plus some principal	The balance can stay high or grow with later draws.
Repayment period	Normally stops	Amortizing principal and interest, a fixed payment, or another contract rule	The first repayment payment can jump, and a low fixed payment can leave a balloon.

The transition depends on more than the rate. Opening balance, future draws, principal repayments, payment rules, phase lengths, and fees all affect cash needs. A fixed repayment amount is not the same as a fully amortizing payment. If it is too small to retire the balance over the stated term, money remains due at the end.

Monthly conventions also differ by lender. A planning ledger that uses annual rate divided by 12 and start-of-month events will not exactly reproduce a statement based on daily balances, rate-change dates, payment floors, promotional periods, or lender-specific posting order. The agreement and current statement remain the controlling sources.

Falling behind on debt secured by a home can lead to foreclosure. Treat a modeled payment as budgeting evidence, not an approval, payoff quote, legal interpretation, or recommendation to borrow.

How to Use This Tool:

Use one current agreement and one dated index value so the term, rate limits, payment rules, and events describe the same line of credit.

Enter the Agreement start month, Credit limit, Opening balance, and the draw and repayment periods in whole months.
Copy the Current index, Contract margin, Rate floor, and Lifetime rate cap from the agreement or a current source. Enter a Stress change in percentage points for comparison.
Choose the Draw-period payment rule. Under interest plus fixed principal, enter the principal amount paid with each draw-period interest payment.
Choose a fully amortizing or fixed Repayment-period rule. Enter the fixed monthly payment only when that is the rule you want to test.
Add dated draws and principal repayments when the balance will change during the schedule. Draws must occur inside the draw period and cannot take the modeled balance above the credit limit.
Open Advanced for upfront, annual, or per-draw cash fees. These fees increase cash paid but do not increase the modeled line balance.
Read the last draw payment, first repayment payment, payment change, and ending balloon together. Then compare the monthly ledger and assumptions with the lender's agreement and statement.

Interpreting Results:

Payment shock is the first repayment-period payment minus the final draw-period payment. A positive amount shows the immediate modeled increase. It does not capture every future rate reset, and a small transition does not prove the plan is affordable over the full term.

Effective APR is index plus margin after the entered floor and lifetime cap. It is held constant inside each scenario.
Repayment start balance is the amount left when draws stop. This is the balance the amortizing payment uses.
Ending balloon is debt still outstanding after the last modeled month. Any value above zero needs a payoff, refinance, sale, or other plan outside this schedule.
Maximum balance reveals whether dated draws push utilization higher than the opening balance suggests.
Total cash payments includes scheduled payments, event principal repayments, and modeled cash fees.

Compare the baseline, stress change, and contract-cap scenarios as sensitivity checks. The cap case shows the entered maximum-rate assumption, not the date or probability of reaching that rate.

Technical Details:

The model advances one calendar month at a time using integer cents and rates rounded to whole basis points. Dated draws or principal repayments are applied at the start of the month, interest is calculated on the resulting balance, and the selected phase payment is applied afterward.

Formula Core:

The effective annual rate is bounded by the entered contract floor and lifetime cap. Monthly interest uses one twelfth of that annual rate. A fully amortizing repayment payment is calculated once at the start of repayment.

\begin{array}{rcl} r_{effective} & = & \min (r_{cap}, \max (r_{floor}, r_{index} + r_{margin})) \\ I_{t} & = & B_{t} \times \frac{r_{effective}}{12} \\ M & = & \frac{B q}{1 - {(1 + q)}^{- N}} \end{array}

Here B_t is the balance after that month's dated events, I_t is monthly interest, q is the effective annual rate divided by 12, N is the repayment-month count, and M is the level amortizing payment. If the rate is zero, M is the repayment-start balance divided by N.

Mechanism Core:

Order of HELOC monthly ledger calculations
Order	Monthly action	Balance or cash effect
1	Apply dated draw or principal repayment	A draw raises balance; repayment is limited to the amount owed.
2	Calculate interest	Interest is rounded to the nearest cent from the post-event balance.
3	Apply phase payment	Draw payment pays interest and optional fixed principal; repayment follows the chosen rule.
4	Add cash fees	Upfront, annual, and per-draw fees increase cash payment without increasing balance.
5	Record ending balance and available credit	The next month begins from the unrounded integer-cent balance.

Under the amortizing rule, the final payment is adjusted to clear the remaining balance and interest. Under the fixed-payment rule, each payment is limited to the balance plus interest; a payment that does not retire the debt leaves an ending balloon.

Limitations:

This is a monthly planning model, not an official lender calculation.

It does not fetch a live index or predict future rates.
It omits daily-balance interest, teaser periods, rate-adjustment timing, periodic caps, fixed-rate subaccounts, late fees, penalties, payment floors, escrow, taxes, and insurance.
It does not calculate official disclosure APR, underwriting, available home equity, payoff amounts, or tax treatment.
Actual agreements may suspend draws, require minimum advances, or use payment rules not represented here.

Worked Examples:

A fixed payment that leaves a balloon

A $5,000 opening balance receives a $2,000 draw, a later $500 principal repayment, and two months of $1,000 fixed repayment payments at an 8% effective annual rate. After $60 of modeled fees and $166.95 of interest, the schedule still ends with a $4,377.61 balance. The fixed payment controls monthly cash outflow; it does not guarantee full amortization.

References:

What is a home equity line of credit (HELOC)?, Consumer Financial Protection Bureau.
What You Should Know About Home Equity Lines of Credit, Consumer Financial Protection Bureau.
Regulation Z § 1026.40: Requirements for Home Equity Plans, Consumer Financial Protection Bureau.

HELOC Payment Calculator

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Payment outlook

How this estimate is built:

How to Use This Tool:

Interpreting Results:

Technical Details:

Formula Core:

Mechanism Core:

Limitations:

Worked Examples:

A fixed payment that leaves a balloon

References: