Useful next calculations
When to use this calculator
- Before comparing mortgage products, brokers or repayment types.
- When you want to test how a different deposit, rate or term changes the payment.
- When you need a quick estimate before using a formal illustration or agreement in principle.
- When you are stress-testing your budget against a higher rate.
A worked example
These are the example figures the calculator opens with.
| Input | Value |
|---|---|
| Current Home Value ($) | $400,000 |
| Outstanding Mortgage Balance ($) | $250,000 |
| HELOC Interest Rate (%) | 8.5% |
| Amount to Draw from HELOC ($) | $0 |
For those figures the calculator returns:
- Current home equity: $150,000.00
- Equity %: 37.50%
- Current LTV: 62.50%
- Max HELOC available: $90,000.00
- Monthly payment: $0.00
- Total interest: $0.00
How to read your results
Current LTV
Loan-to-value is the mortgage as a percentage of the property value. Crossing common LTV bands can change product eligibility and pricing.
Monthly Payment
Estimated monthly mortgage repayment under the rate, term and balance you entered. Compare it with a lender illustration before you apply.
Total Interest
Additional amount paid above the original principal during the term, using the rate you entered. Fees and early-repayment charges are not included unless you added them.
Method & assumptions
This calculator determines your current home equity and loan-to-value ratio, then estimates the maximum HELOC credit line your lender may offer based on the combined loan-to-value (CLTV) percentage you enter. The default 85% CLTV reflects the most common threshold used by major US lenders as of 2024, though some lenders allow up to 90% and others cap at 80%. Maximum HELOC availability equals (home value × max CLTV) minus your current mortgage balance. The monthly payment figure assumes the drawn amount is repaid in fully amortizing equal installments over the repayment period at the stated fixed rate; actual HELOCs typically carry variable rates tied to the Wall Street Journal prime rate, so real payments will fluctuate with rate changes.
The total interest calculation reflects the full repayment period and does not model the interest-only draw period that most HELOCs include before repayment begins, nor does it account for annual fees, closing costs, or inactivity fees that some lenders charge. Home value should reflect a realistic current market estimate, not the original purchase price or tax-assessed value. An independent appraisal or broker price opinion will be required by the lender and may differ from estimates produced by automated valuation models. Always obtain a formal Loan Estimate from your lender before making borrowing decisions.
Common mistakes
- Mixing up loan amount and property value, which distorts affordability and LTV.
- Using a headline rate but forgetting fees, insurance or repayment type.
- Testing only one term length instead of comparing payment and total cost together.
- Treating the result as a lender decision rather than a planning estimate.
What to do next
- Run a second scenario with a cautious assumption so you can see the downside clearly.
- Compare the result with the related calculators below before making a decision.
- Check current local rules, eligibility and provider terms before applying or committing money.
- Keep a record of the assumptions so you can update the estimate when a quote, bill or pay figure changes.