First and foremost don't trust the values you see on the public real estate sites. To get the most accurate and up to date value on your home, contact an agent in your area and ask them to provide to with a comparative market analysis.
For any homeowner it's wise to have a realtor meet with you to give you a free market analysis. The realtor would be able to preview your property and advise you appropriately. The value of your home is based on comparable sales in your neighborhood within a 3-6 month period. Properties that were sold which were similar to your home would be a comparable sale. This is mainly what the appraisers use to base a value. I hope this helps. Thank You in advance.
There are several ways a) free market evaluation by an agent
* b) pay a licensed appraiser.
c) the only way that can know for sure is the licensed appraiser. All of the websites and realtors can "guesstimate"