Somebody sends me their square footage and a price per square foot they found online, multiplies the two, and asks whether that is what their house is worth. I get that question almost every week. The answer is almost always no.
Not because the arithmetic is wrong. Because price per square foot does not behave the way people assume it does.
Start with how far apart the numbers sit inside one region. In the most recent county figures, Arlington was selling at about $498 a square foot and Alexandria at $517. Fairfax County was $360. Loudoun was $294. Prince William was $256, and Stafford was $204. (Source: Bright MLS, spring 2026.)
That is all Northern Virginia. The same house, the same size, the same finishes, is worth more than twice as much per foot in one of those places as in another. The building is not different. The ground under it is.
Most people expect that much, at least roughly. Here is the part that surprises almost everyone.
In Loudoun County this spring, detached single-family homes sold at about $291 per square foot. Townhomes and condos sold at about $303. The smaller attached homes carried the higher price per foot, not the lower one. (Source: Bright MLS via DAAR, April 2026.)
That is not a data error. It is how houses actually price. Every home has a floor of value that has very little to do with size. One kitchen. Two or three bathrooms. A furnace, a water heater, a roof, a lot with utilities run to it. A 1,400 square foot townhome carries all of that across 1,400 feet. A 4,200 square foot colonial spreads the same fixed costs over three times the space, and most of the extra footage is bedrooms and finished basement, which are the cheapest feet in any house.
So inside the same market, price per foot generally falls as homes get bigger.
Which is why the number cuts both ways. Take a county average and apply it to a large home, and you can talk yourself into a price the market will not pay. Apply it to a townhome or a smaller house, and you can leave real money on the table.
Then there is the neighborhood layer. This spring in Loudoun, Sterling Park sold at about $323 a foot, Ashburn Farm at $310, Brambleton at $299, Ashburn Village at $298, Cascades at $296, and Broadlands South at $292. That is a spread of roughly 10 percent among communities sitting within a few miles of one another, and the countywide $294 does not describe any single one of them well. (Source: Bright MLS, spring 2026.)
I am not telling you to throw the number away. Price per square foot does one job well: comparing your home to three or four homes of similar size, in your neighborhood, that sold recently. Stretched wider than that, it stops being information and starts being noise.
The way I handle it is to pull the actual sales that resemble your home in size, age, and condition, adjust for the real differences between them and yours, and let those set the range. Square footage is one input. It is not the calculation.
If you have run that math on your own place and want to know how far off it landed, call me at 571-496-9009. I will show you what your house looks like against real sales, and I will tell you straight if the number you already had was close.