How the heloc calculator works
Enter your home’s value, your mortgage balance, how much you plan to draw and the HELOC rate. The calculator shows your equity, your combined loan-to-value after the draw, the most you could borrow at an 80% combined loan-to-value, and the interest-only monthly payment during the draw period.
The formula
Equity = home value − mortgage balance; combined LTV = (mortgage + draw) ÷ home value; available at 80% CLTV = 80% × home value − mortgage; draw-period payment = draw × rate / 12.
Most HELOCs are interest-only during the draw period and then switch to principal-and-interest payments, which are higher. Lenders set their own loan-to-value limits; 80% is a common one, not a rule.
Frequently asked questions
How much can I borrow with a HELOC?
Many lenders cap your combined loan-to-value at around 80%. The calculator shows 80% of your home’s value minus your mortgage balance.
Why is the payment interest-only?
During the draw period most HELOCs only require interest. The payment rises once repayment of principal begins.
What is combined loan-to-value (CLTV)?
Your mortgage plus your HELOC, divided by your home’s value.
Results are estimates for planning, not financial advice. Last reviewed 2026-09-28.