How this HELOC interest calculator works
Most HELOCs split into two chapters. While you can still draw, many lenders only ask for interest on what you have actually used. Later, the line often switches to a fixed-term payoff where each bill chips away at principal. This tool follows that pattern with the formulas noted in the JavaScript source — handy when you are comparing a quote against a napkin math check.
Draw-period interest-only
Monthly interest-only estimate = drawn balance × (APR ÷ 12). If your line is unused, interest is zero. Extra principal payments are not assumed.
Repayment fully amortizing EMI
We use the standard amortizing payment formula M = P × r × (1+r)n / ((1+r)n − 1), where P is the balance entering repayment, r is the monthly rate, and n is repayment months. That EMI is what many people mean when they search for a “HELOC interest calculator” or “HELOC payment calculator.”
CLTV and equity room
CLTV = (first mortgage + HELOC drawn) ÷ home value. The equity-room sketch applies your max CLTV percentage and remaining credit limit. Lenders apply their own rules; treat this as a planning aid only.
What this tool does not do
- No live rate API, rate board, or “today’s HELOC rates” widget
- No loan application, soft pull, or lender marketplace
- No guaranteed approval, APR, or payment
HELOC calculator FAQ
What is a HELOC interest calculator?
A HELOC interest calculator estimates interest-only payments during the draw period and fully amortizing payments during repayment, based on the balance, APR, and term lengths you enter.
How is HELOC interest calculated during the draw period?
During a typical interest-only draw period, the monthly interest estimate is drawn balance × (APR ÷ 12). Principal usually does not decline unless you make extra payments.
What happens in the HELOC repayment period?
After the draw period, many HELOCs convert to fully amortizing payments. This tool uses the standard EMI formula so principal and interest are paid down over the repayment term you enter.
Does this site use live bank rates?
No. APR is always user-entered. We never display live lender rate boards or claim to offer loans.
What is CLTV and why does it matter?
Combined loan-to-value (CLTV) compares your first mortgage plus HELOC balance against home value. Lenders often use CLTV ceilings when sizing available credit; our equity-room figure is illustrative only.
Is this a loan offer or financial advice?
No. Results are educational estimates only. They are not a loan offer, credit decision, or personalized financial, tax, or legal advice. Confirm figures with a licensed lender or advisor.
HELOC vs home equity loan — which calculator should I use?
Use the HELOC calculator for revolving credit with a draw then repayment phase. Use the home equity loan calculator for a fixed lump-sum loan that amortizes from day one.
Will my real payment match this estimate?
Possibly not. Fees, variable rates, payment floors, credit line freezes, taxes, and lender rules can change payments. Treat outputs as a planning sketch.