The amount of equity you currently have in your home will determine your Home Equity Line of Credit (HELOC) limit. You must retain at least 10% of the value of the equity in your home (sometimes referred to as a 90% LTV maximum). You can make a ballpark estimate of your HELOC maximum by calculating what 90% of your homeâ€s value is, then subtracting your existing mortgage balance(s) from that number.