Why does my HELOC payment change later?

A HELOC has two phases. During the draw period you usually pay interest only, so the payment is small. When the draw period ends the balance has to amortise over the repayment period, which adds principal. That difference is the payment jump.

How much can I borrow with a HELOC?

Lenders cap combined debt at a share of the home's value (CLTV). Your available line is that cap minus the balance still owed on the first mortgage.

Is a HELOC cheaper than a credit card?

Compare interest rather than payments: the credit-card interest on the balance versus the HELOC interest on the same balance, monthly and yearly.

What happens to a HELOC if rates rise?

Most HELOC rates float. Adding the rise you want to survive to the APR gives the stressed interest-only payment and the extra monthly cost.

HELOC calculator: the payment jump nobody shows you

Nine numbers in. Sixteen answers out — your credit line, the cheap interest-only payment during the draw period, the bigger principal-and-interest payment after it, and what happens if the rate climbs.

Example numbers are pre-filled so you can see it working. Replace them with yours — everything recalculates as you type.

Your inputs

Home appraised value

Current 1st mortgage balance

Lender max CLTVThe share of your home value the lender lets all your debt reach. 85 means 85%.

Amount you plan to draw

HELOC annual interest rate (APR)

Draw period length (years)

yrs

Repayment period length (years)

yrs

Credit-card APR you'd pay off

Rate rise to stress testHELOC rates float. This is the increase you want to survive.

Now — interest only

—

during the draw period

Later — principal & interest

—

once the draw period ends

—

Equity & credit line

What a lender will actually offer

Payments & lifetime cost

The two payments every HELOC really has

Consolidation & rate shock

Does it beat the credit card, and what if the rate climbs?

Take these numbers with you

Your result above is already complete and always free. If you want a spreadsheet you can keep and re-run every time your rate moves, we'll send the free starter workbook: the Inputs tab and the Equity & Credit Line tab, 6 live formulas, yours to type your own figures into.

Your numbers never leave your browser — every calculation on this page runs on your device. The only thing we ever send is the email address you type here, and one click unsubscribes.

Want the full four-sheet workbook?

This page is one slice of it. The paid version is the spreadsheet itself — 16 live cross-sheet formulas, so you change one input and all four tabs recalculate:

Inputs — the nine cells you edit
Equity & Credit Line — 6 results
Payments & Lifetime Cost — 6 results, including the PMT amortisation
Consolidation & Rate Shock — 4 results

Works in Excel, Google Sheets and Numbers. $39, one payment, yours to keep.

Get the full HELOC workbook — $39

Questions this calculator answers

Why does my HELOC payment change later?: A HELOC has two lives. During the draw period you usually pay interest only, so the payment is small. When the draw period ends the balance has to amortise over the repayment period, which adds principal. The "payment jump" line above is exactly that difference.
How much can I borrow?: Lenders cap your combined debt at a share of the home's value (CLTV). Your line is that cap minus what you still owe on the first mortgage — the "Estimated HELOC credit line available" row.
Is a HELOC cheaper than my credit card?: Compare interest, not payments. The consolidation rows put the credit-card interest on your balance against the HELOC interest on the same balance, monthly and yearly.
What if the rate goes up?: Most HELOCs float. Set the stress-test rise to the increase you want to survive and read the stressed interest-only payment and the extra monthly cost.

This is a calculator, not financial advice. Your lender's payoff figure, fees and CLTV cap are the ones that count — check them before you apply.

Car refinance calculator · All free tools · ReadyStack
Free, no signup, no tracking of your figures. Nothing on this page is stored.