Please see “Factors That Influence Your Home’s Value” to realize that there are many, many things that are relevant to what your home is worth.
Add to those the current market in your area. What are the trends, economic outlook, and current health of those industries that affect your area? What has sold in your town, neighborhood, and street recently, and in what way do they compare to your home?
It is not an easy thing to judge objectively and there is no mathematical or straightforward process to give you the answer. This is why the researched opinion of a professional is of utmost importance.
If possible, do some homework on your own. Check out which homes have sold in your area. You can do this by going to Listingbook which has all the sold homes AND all the photos of the interior. From there you can see if the kitchen and baths are up to date.
You can also go to weekend Open Houses in your area where you can see the homes inside and out and understand what is being offered for what price. What I recommend you NOT do is go to the various Real Estate websites that claim to tell you what your home is worth. All of these use some formula on area sales which are simply unreliable in assessing the market value of your particular home.
My recommendation is to get three market appraisals from experienced agents. Listen carefully to what they say about your home, the specific homes they use as the best comparables, and why. Good agents will know these homes, literally inside and out. Try to adapt the “buyers” viewpoint and try to stay objective. Look at the comparable homes in size, property size, and condition. Average the suggested prices of the three appraisals to get a good idea of what your home is worth.
The only exception to this approach is if the material of one of the professionals you interview is so thorough that the price of your home is apparent to you all. This does happen.