This^^^
And if you want to get more technical, then you can take the home value and multiply it by .94, if you would likely use a realtor to sell it eventually, which generally ends up meaning you pay about a 6% commission in the US.
For example, the zillow estimate of my home is 282,000, which from other home sales in the neighborhood is probably very accurate. However, if I were to list with a realtor, I'd get about 263,000 after all the realtor fees and closing costs are factored in. And I have 150k left on the note, so I could use 132k or 113k as my home equity, depending on how I want to look at it.