HELOC Calculator

HELOC Calculator

A HELOC calculator (Home Equity Line of Credit) estimates payments on a revolving credit line secured by your home equity. HELOCs have a draw period (typically 10 years) followed by a repayment period.

HELOC vs Home Equity Loan

Feature	HELOC	Home Equity Loan
Type	Revolving credit	Lump sum
Rate	Variable	Fixed
Draw Period	Yes (5-10 years)	No
Best For	Ongoing expenses	One-time need
Interest	Only on used amount	On full amount

HELOC Payment Examples

$50,000 credit line at 8% variable rate:

Amount Used	Interest-Only (Draw)	Full Repayment (15yr)
$10,000	$67/month	$96/month
$25,000	$167/month	$239/month
$50,000	$333/month	$478/month

HELOC Calculator Implementation

``javascript function calculateHELOC(amountUsed, rate, drawPeriodYears, repaymentYears) { const monthlyRate = rate / 100 / 12;

// Interest-only payment during draw period const interestOnly = amountUsed * monthlyRate;

// Full repayment after draw period const repaymentMonths = repaymentYears * 12; const fullPayment = amountUsed * monthlyRate / (1 - Math.pow(1 + monthlyRate, -repaymentMonths));

return { interestOnlyPayment: interestOnly.toFixed(2), fullPayment: fullPayment.toFixed(2), totalInterestOnly: (interestOnly * drawPeriodYears * 12).toFixed(2), totalFullRepayment: ((fullPayment * repaymentMonths) - amountUsed).toFixed(2) }; }

console.log(calculateHELOC(50000, 8, 10, 15)); // { interestOnlyPayment: '333.33', fullPayment: '477.83' } ``

HELOC Considerations

HELOCs have variable rates that can increase significantly. Your home is collateral—defaulting means foreclosure. Use HELOCs for value-adding projects (renovations) rather than consumption (vacations).

Where the Money Goes

On $50,000 at 8% over 10 years, paying $607 a month:

Point	Principal repaid	Interest paid	Balance
Year 1	$3,403	$3,877	$46,597
Year 3	$9,043	$9,156	$40,957
Year 5	$20,082	$16,317	$29,918
Year 8	$33,555	$21,043	$16,445
Year 10	$50,000	$22,797	$0

Early payments are mostly interest. That is not a fee structure — it is arithmetic: interest accrues on the outstanding balance, which starts at its largest. It is also why an extra payment made early saves far more than the same payment made late.

What a Rate Change Costs

Rate	Monthly	vs 8%	Total repaid
7.00%	$581	-$26	$69,665
7.50%	$594	-$13	$71,221
8.00%	$607	—	$72,797
8.50%	$620	+$13	$74,391
9.00%	$633	+$27	$76,005

Half a percentage point moves the monthly payment by $13 and the total by $1,595. Shopping three lenders usually beats any amount of negotiating on price.

What an Extra Payment Buys

Every dollar above the required $607 goes entirely to principal, which removes all the future interest that principal would have accrued:

Extra per month	New payment	Paid off in	Interest saved	Time saved
$50	$657	8 yr 11 mo	$2,776	13 months
$100	$707	8 yr 1 mo	$4,933	23 months
$250	$857	6 yr 3 mo	$9,256	45 months
$500	$1,107	4 yr 6 mo	$13,104	66 months

The returns are non-linear because the saved interest compounds. It is also front-loaded: the same extra payment made in year one saves substantially more than in the final year, because it removes principal that would otherwise accrue interest for the whole term.

Before Paying Extra

• Check for a prepayment penalty. Uncommon on mortgages now, still present on some auto

and personal loans.

• Tell the servicer to apply it to principal. Many default to holding it as the next

scheduled payment, which achieves nothing.

• Compare against the alternative. Paying down 8% debt is a guaranteed

8% return. If you hold debt at a higher rate, or an employer match you are not taking, those come first.

• Keep the emergency fund. Money paid into a loan is not retrievable without

refinancing. Liquidity has value that an interest calculation does not show.