Home Value by Square Foot:

One of the biggest determining factors in determining comparable value is square footage.
When comparing the square footage of homes always try to keep comps as similar in square footage as possible. Figuring out the price of a home on a square footage basis is an excellent way to compare apples with apples. It becomes more complicated when one home has been renovated and another needs work. Don't compare a newly built home's price per square foot with an older home's price per square foot.
There's Square Footage and There's Square Footage
A square foot is defined as a two-dimensional square measuring one foot on each side. If you are looking at a home that seems a little smaller than the stated square footage, it might not be your eyes. Real estate brokers tend to measure square footage by inside room dimensions. Developers like to measure the exterior of the building. This can add considerable square footage to the home.
You also need to find out exactly what has been factored into the equation. Does the total measurement include basement space? Garage space? Deck space? Space on staircases? There's no standard way to measure square footage. Sellers will include every nook and cranny and buyers won't.
Do not solely compare the size of the land the property sits on and the price of the property. Lots sell for different prices than homes and the cost varies greatly from neighborhood to neighborhood. For example, if the house is in terrible shape, or is considered a "tear-down," a developer may only want to pay for the price of the lot, since tearing down and hauling away the existing structure is an added expense.
Side-by-Side Comparison
In some areas of the country, agents do not want to be liable for representing a total square footage of the property. Total square footage is not indicated on the listing sheet, but room dimensions are shown. The room count may not include bathrooms, hallways, closets, and other spaces. You might have to compare every room side by side and guesstimate total size.
In this instance, estimate the total square footage by multiplying the dimensions of each room. For example, if the bedroom is 10 feet by 12 feet, then the area, or square footage, is 120 square feet. Add up all of the room dimensions for a total square foot measurement. You may still have to estimate hallways and other spaces, but it gives you a good estimate.
After determining the size of the home you desire, the equation is simple. Just divide the listing price by the number of square feet and you will get the price per square foot. For example, a 1,000-square-foot condo priced at $300,000 costs $300 per square foot.
It's always to your advantage to buy a home with a reasonable cost per square foot. A home with a square footage cost lower than other homes in the neighborhood might be a great deal. On the other hand, the home may have a lot of other things wrong with it that need renovation, and unless you had remodeling in the budget, it might not be worth it to you.