As recommended if you are concerned about the sq. ft. Have someone check the tax records to see if that is correct. As a general you know garages or unfinished space is not calculated into living space. Even though there may be some value to a buyer the tax records won't show it as sq. ft.
What is your intention to knowing the value of your home?
Have an amazing day!
Coldwell Banker - Los Altos Office
Below is some explanation from Trulia on how they determine values. In it they admit there can be a 20% variance. When you changed your sq ft a whole different set of recent sales were likely looked at by their algorithm.
If you are looking for an accurate valuation of your home, let me know off line and I will be happy to send you a market value analysis in the next 24hrs!
If you are concerned about what value Trulia shows and want to try to correct it or "game" it, let me know, between us and Trulia, I think we can find a way to get it to be more accurate.
If you are thinking about getting ready to sell your place some time this year, you can learn a little more about me at these links
Then call me so we can discuss how to achieve your specific objectives.
"A Trulia Estimate is just that: an estimate of a home's worth. Our estimates use a ton of info, including recent sales of similar homes and home facts like number of bedrooms and bathrooms, square footage, and more to provide insight into what a home is worth. You can help us improve our accuracy by telling us what you think of your homeâ€™s Estimate, and by claiming your home and updating its facts... We measure accuracy by comparing (1) actual sales prices for recently sold homes over a 3 month period with (2) those homesâ€™ Estimates at the start of that 3-month period. For each county, we report the median error of these differences and the percentage of sales where Trulia Estimates were within 5%, 10% and 20% of the final sale prices...."
The above and more can be found at Trulia's website at this page http://www.trulia.com/trulia_estimates/
I find valuations such as this to be items of curiosity, only. Anyone can type in an address to one of the valuation sites and get back a figure on any house in which they have an interest. Whether the interest is legitimate or one of curiosity, only, is unknown. Personally, what others find about the value of my home is not of importance to me.
If, however, I wanted to know the MARKET value of my home because I was planning on selling it or borrowing against it I would talk to the expertsâ€¦Realtors or appraisersâ€¦and not worry about what an automated valuation site says.