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HELOC calculator

Both payments on a home equity line, plus the one at your contract rate ceiling that federal law requires your lender to disclose.

Inputs
What you owe on the line. Interest is charged on this, not on the whole credit limit.
A HELOC is usually prime plus a margin. The Federal Reserve put prime at 6.75% for the week ending 17 July 2026.
The ceiling written into your contract. Regulation Z requires one to exist and be stated. Navy Federal publishes 18%.
Minimum payment during the draw periodInterest only is the common minimum, and it repays no principal at all.
More options
Commonly 80% or 85% of the home value, counting the first mortgage.
Result
Payment at your rate ceiling
$1,157
Draw period payment
$531
Repayment period payment
$651
Jump when the draw ends
$120
Jump as a percentage
22.52%
Ceiling payment above today
$626
Reg Z disclosure, $10,000 at the ceiling
$150
Balance when the draw ends
$75,000
Principal repaid during the draw
$0
Total interest over the plan
$144,958
Line your equity supports
$145,000

Key takeaways

  • On $75,000 at 8.5% the interest-only draw payment is $531.25 and the repayment payment is $650.87, a jump of 22.52%.
  • At an 18% contract ceiling the repayment payment is $1,157.48, which is 2.18 times what the borrower pays during the draw.
  • Regulation Z at 12 CFR 1026.30 requires the contract to state a maximum rate, and 1026.40(d)(12)(x) requires the payment at that rate on a $10,000 balance to be disclosed.
  • Ten years of interest-only payments cost $63,750 and leave the $75,000 balance untouched, with total plan interest reaching $144,958.
  • Paying principal and interest during the draw costs $45.44 more a month, removes the payment jump, and saves $12,352 of interest.

How a HELOC actually charges you

A HELOC is a revolving credit line secured against your home, split into a draw period when you can borrow and usually pay interest only, and a repayment period when the balance amortises. The CFPB puts the distinguishing feature plainly: unlike a home equity loan, a HELOC usually carries an adjustable rate. Most are quoted as prime plus a margin, and the Federal Reserve put the bank prime loan rate at 6.75% for the week ending 17 July 2026.

Draw $75,000 at 8.5% with a 10-year draw and a 20-year repayment and you pay $531.25 a month at first. When the draw ends that becomes $650.87, a rise of 22.52%.

The payment your contract already permits

Every HELOC contract carries a maximum interest rate, because federal regulation requires one. Under Regulation Z at 12 CFR 1026.30, a dwelling-secured variable-rate contract must state the highest rate that may be imposed over its term, in a form the borrower can work out at signing. Navy Federal publishes a ceiling of 18% and a floor of 3.99%.

That ceiling is the number worth knowing, and it is missing from every HELOC calculator we fetched. calculator.net states outright that it does not model a variable rate. calc.one is more candid still, saying a variable rate makes total interest unknowable in advance, and then leaves the reader without the bound the contract provides. heloctool.com discusses rate caps and applies them to nothing.

On $75,000, 20-year repaymentPayment
Draw period today, interest only$531.25
Repayment at today's 8.5%$650.87
Repayment at an 18% ceiling$1,157.48

The worst case your contract allows is 2.18 times what you're paying now. Forecasting the rate is impossible, but that boundary is already written into the agreement you signed.

The $10,000 figure on your disclosure

Regulation Z requires your lender to tell you the minimum payment at the maximum rate, computed on a $10,000 balance. The requirement sits at 12 CFR 1026.40(d)(12)(x), alongside 1026.40(d)(12)(ix) which requires the maximum APR itself, and a rule that variable plans carry a 15-year historical example of how the index has moved.

At an 18% ceiling with an interest-only minimum, that figure is $150 a month. This calculator computes it on your own numbers so you can hold it against the paperwork.

What the interest-only decade costs

Interest only means no principal, so the balance that arrives at the repayment period is every dollar you drew. Ten years of $531.25 payments come to $63,750, and the $75,000 is exactly where it started. Total interest across the whole plan reaches $144,958, close to double the amount borrowed.

Regulation Z anticipates this. Under 12 CFR 1026.40(d)(5), a lender must warn where minimum payments may not repay principal, and state that a balloon payment may result.

Switch the draw minimum to principal and interest and the arithmetic changes sharply. The payment goes from $531.25 to $576.69, a difference of $45.44. The balance falls to $66,452 by the time the draw ends, the payment jump disappears entirely because the loan amortises continuously, and total interest drops to $132,607. That's $12,352 saved for $45 a month.

Where the numbers come from

The draw payment on an interest-only minimum is the balance times the monthly rate. The repayment payment amortises whatever balance survives the draw over the repayment months, using M = P times r times (1 + r) to the power n, divided by (1 + r) to the power n minus 1. The ceiling figures run the identical calculation at the contract maximum instead of today's rate.

Line sizing uses combined loan to value, which counts your first mortgage against the home value. At 85% CLTV on a $500,000 home with a $280,000 mortgage the headroom is $145,000. Fetched limits vary: 80% at Firstrust, up to 85% at Bank of America for primary residences on lines under $500,000, 80% recommended by Navy Federal.

One thing this does not do is predict the rate. Nobody can, and a calculator that pretends otherwise is selling certainty it doesn't have. What it can do is price the two ends of the range your contract defines.

What this does not decide for you

This models a credit line's mechanics. It cannot tell you whether borrowing against your home is wise, what rate you'd be offered, or how prime will move. Your margin over the index, your cap, your draw terms and any annual fee are in your own agreement and vary by lender. The CFPB is blunt about the stake: fail to repay a HELOC and the lender can foreclose on your home. Treat these figures as arithmetic, not advice, and talk to a licensed professional about your own file.

Frequently asked questions

What is a HELOC? A HELOC is a revolving line of credit secured against your home, with a draw period when you can borrow and usually pay interest only, followed by a repayment period when the balance amortises. Per the CFPB, unlike a home equity loan a HELOC usually carries an adjustable rate, and when the draw period ends you may have to repay the balance over a set period or in one payment.

What happens to my payment when the draw period ends? It jumps, because principal starts being repaid. On a $75,000 balance at 8.5% with a 10-year draw and a 20-year repayment, the interest-only payment of $531.25 becomes $650.87, a rise of $119.62 or 22.52%. The balance entering the repayment period is the full $75,000, because an interest-only minimum repays no principal at all.

How high can my HELOC payment legally go? As high as the rate ceiling in your contract allows, and that ceiling is not optional. Regulation Z at 12 CFR 1026.30 requires a dwelling-secured variable-rate contract to state the maximum rate that may be imposed over its term. At an 18% ceiling of the kind Navy Federal publishes, the repayment payment on $75,000 is $1,157.48, which is 2.18 times the $531.25 being paid during the draw.

What is the $10,000 disclosure my lender gave me? It is the minimum periodic payment at your maximum rate on a $10,000 balance, required by 12 CFR 1026.40(d)(12)(x). At an 18% ceiling with an interest-only minimum that figure is $150 a month. This calculator computes it on your own numbers so you can check it against the disclosure.

How much does the interest-only period actually cost? On the default figures, $63,750. Ten years of interest-only payments at $531.25 leave the $75,000 balance exactly where it started, and total interest across the whole plan reaches $144,958, nearly double the amount borrowed.

Should I pay principal during the draw period? The arithmetic is straightforward even though the decision is yours. Switching the draw minimum from interest only to principal and interest raises the payment from $531.25 to $576.69, a difference of $45.44, and it removes the payment jump entirely because the balance amortises continuously. Total interest falls from $144,958 to $132,607, a saving of $12,352.

How much can I borrow on a HELOC? Lenders size the line against combined loan to value, which counts your first mortgage. At 85% CLTV on a $500,000 home with a $280,000 mortgage, the headroom is $145,000. Fetched limits vary: 80% at Firstrust, up to 85% at Bank of America for primary residences under $500,000, and 80% recommended by Navy Federal.

Sources

Part of Real estate calculators, which compares all 15 and says which answers what.

Built and reviewed by DexTechLabs against the primary sources cited above. Last reviewed 2026-07-21. How we build and verify tools.

Mutual fund returns are market-linked and not guaranteed, so this is an estimate, not investment advice. Consult a SEBI-registered adviser before acting on it.