THE NUMORIX GUIDE
How to use the Home Equity Loan Calculator
Last reviewed September 14, 2026
What this calculator does
The route calculates equity as home value minus mortgage balance, then sets maximum loan to 80% of that equity and uses that maximum as the modeled loan amount.
Formula and method
The route calculates equity as home value minus mortgage balance, then sets maximum loan to 80% of that equity and uses that maximum as the modeled loan amount. It applies the fixed-rate mortgage formula to that loan for the selected term, then reports total interest and total cost. The credit-score input is displayed but is not used by the current engine.
Variables and inputs
Enter home value, current mortgage balance, credit score, interest rate, and loan term of 10, 15, 20, or 30 years. Values are dollars except credit score and annual interest rate. The engine does not provide a separate requested-loan field; it models its equity-based maximum.
Worked example
With a $400,000 home and $200,000 mortgage balance, equity is 400,000 - 200,000 = $200,000. The route's 80% equity limit is 200,000 x 0.80 = $160,000, which becomes the modeled loan. At 8% for 15 years, r = 0.08 / 12 and the payment formula gives about $1,529 per month.
How to interpret the result
The displayed maximum is a mathematical equity limit used by this page, not an approval amount. A home-equity loan is secured by the property, so the payment and the risk of missed payments should be considered with the existing mortgage and household budget.
Common mistakes to avoid
Do not confuse equity with cash available after selling costs. Do not assume 80% of equity is the same as an 80% combined loan-to-value limit. Remember that the credit-score field does not currently alter this route's result.
Assumptions and limitations
The engine uses 80% of equity, not a lender's combined-LTV calculation, and ignores credit score, income, first-lien balance rules, fees, taxes, insurance, variable pricing, and requested loan size. Actual underwriting may allow less or none.