A quick way to evaluate what you may have available in a home equity loan would be to obtain a value from a resource such as Zillow and multiply that value times 80%. 

You would then subtract your first mortgage from the resulting amount to obtain a rough estimate of the amount that may be available to you with a home equity loan or Home Equity line of credit.

It’s important to remember that this is only an estimate of the amount available. Using a lower percentage of your home’s value can save both time and fees associated with obtaining the loan.