Formulas and 2026 figures checked & updated: July 2026
Max approved: $122,500 (85% CLTV)
How to Use the HELOC Calculator
- Enter your home's current value and your existing mortgage balance.
- Enter the credit line you're requesting — the calculator caps it at 85% combined loan-to-value.
- Set what percentage of the line you expect to actually draw.
- Set the draw-period rate and length (often interest-only), and the repayment-period rate and length.
- Compare your draw-period payment to your repayment-period payment.
What This Calculator Does
A HELOC works in two distinct phases, and this calculator models both: an interest-only draw period, where your payment is based only on the balance you've actually drawn against your credit line, and a repayment period, where that balance amortizes like a standard loan.
It also caps your requested credit line at a typical 85% combined loan-to-value (CLTV) limit — your existing mortgage plus the new HELOC — so the numbers reflect what a lender would realistically approve.
Formula
Draw Payment = Drawn Balance × Rate ÷ 12 | Repay Payment = Amortized(Drawn Balance, Rate, Term)- CLTV Cap(Mortgage + HELOC) ÷ Home Value, capped at 85%
Examples
Example: $450,000 home, $260,000 mortgage, $75,000 line, 60% drawn
9% draw rate (interest-only), 10-year draw period, then 15-year repayment at 9%.
Draw-period payment ≈ $338/month; repayment-period payment ≈ $456/month once amortization begins.
Continue Your Financial Planning
Methodology
Maximum line = 85% of home value minus existing mortgage balance. Draw-period payment = amount drawn × draw rate ÷ 12 (interest-only). Repayment-period payment amortizes the drawn balance over the repayment term at the repayment rate. HELOC rates are typically variable — this calculator uses the rates you enter as a fixed assumption for modeling purposes.
Frequently Asked Questions
What's the difference between a HELOC and a home equity loan?+
A HELOC is a revolving line of credit at a variable rate with a draw period — often interest-only — followed by a repayment period where you pay down principal and interest. A home equity loan is a fixed lump sum at a fixed rate with predictable payments from day one. This calculator models a HELOC; use the linked Home Equity Loan calculator for a fixed loan.
How much can I borrow with a HELOC?+
Most lenders cap combined loan-to-value (CLTV) — your first mortgage balance plus the new HELOC line — at 80-85% of your home's current value. This calculator uses an 85% cap by default.
Why is my draw-period payment so much lower than the repayment-period payment?+
During the draw period, most HELOCs only require interest-only payments on whatever balance you've drawn — no principal reduction. Once the repayment period starts, the drawn balance amortizes like a normal loan, which is why the payment jumps.
Is HELOC interest tax deductible?+
Only if the funds are used to buy, build, or substantially improve the home securing the loan, per the 2017 Tax Cuts and Jobs Act. Using a HELOC for debt consolidation, tuition, or other purposes generally isn't deductible — confirm your specific situation with a tax professional.
Can I save my results?+
Yes. Use “Save results” to store a snapshot. Without an account it remains in this browser. If you log in, saved scenarios sync securely to your SmartRates account so they are available on your other devices.
How do I share my calculation?+
Click “Share” in the toolbar to copy a link (or open your device’s share sheet). The link encodes your exact inputs, so whoever opens it sees the calculator pre-filled with the same numbers and the same result.
Can I email my calculator results?+
Yes. Click “Email results” to open your default email application with the current inputs, results, and calculator link already included. Review the message and choose the recipient before sending.
Can I export or print my results as a PDF?+
Yes. Click “Export PDF” to open a clean, printable summary of your inputs and results that you can save as a PDF or print. It includes a timestamp and a link back to the calculator.
How accurate are the calculator results?+
The arithmetic follows the formula and assumptions documented on this page. The result is still an estimate because actual rates, fees, taxes, timing conventions, eligibility rules, and provider calculations can differ. Use figures from your official quote, statement, contract, or tax form before making a financial decision.
Which inputs have the biggest effect on the result?+
Rate, time, starting balance, recurring payments or contributions, and fees usually have the largest effects. Change one input at a time to create a conservative, expected, and optimistic scenario instead of relying on a single forecast.
Are taxes, fees, and inflation included?+
Only when they appear as an input or are explicitly described in the methodology. Do not assume an omitted cost is zero. Review the formula and methodology sections to see exactly what is included before comparing the result with an outside quote.
Can this calculator predict future rates or returns?+
No. A calculator projects the assumptions entered; it cannot predict market returns, inflation, variable interest rates, tax-law changes, or provider decisions. Rerun the calculation with several assumptions to understand the range of possible outcomes.
Why might my lender, bank, broker, or tax software show a different result?+
Professional systems may use daily timing, transaction dates, compounding conventions, rounding rules, account-specific fees, credits, eligibility details, or regulations that a general-purpose calculator cannot know. A small difference can be rounding; a large difference usually means an assumption or included cost is different.
Disclaimer: Calculations are for informational purposes only and do not constitute professional financial advice. Please consult with a certified professional before making financial decisions.