How to Estimate Your Home's Exterior Size for a Washing Quote

Wall area is not floor area

The square footage on a listing or tax record is floor area: the space inside. A house washing quote is based on the outside walls that actually get cleaned. The two numbers are related but not the same. A 1,500 square foot single story home and a 1,500 square foot two story home have very different amounts of wall.

So skip the listing number and measure the outside. It takes a tape measure or a measuring wheel, a notepad and a few minutes.

It also helps to sketch the house. A rough drawing of the outline from above, with each wall labeled, keeps you from missing a segment or counting one twice.

Step one: the perimeter

Walk around the house and measure each wall at ground level, then add them together. For a simple rectangle, that is two long sides plus two short sides. A 50 by 30 foot house has a perimeter of 50 plus 30 plus 50 plus 30, or 160 feet.

For homes with bump-outs, L shapes or courtyards, measure every segment. Including the inside walls of a courtyard or the walls along an attached garage makes a difference, since those get washed too. If you cannot reach a wall, an online map's measuring tool can give you a rough length from above.

Step two: the wall height

For a single story home, measure from the ground to where the wall meets the eave. Wall heights vary, so measure your own rather than assuming. For a two story home, the walls are roughly double. If you cannot reach the top, measure one siding course or a known feature like a door frame, then count how many fit up the wall.

Multiply perimeter by height. The 160 foot perimeter at 9 feet tall gives 1,440 square feet of wall.

Step three: gables and odd shapes

Gable ends, the triangles under a pitched roof, add area. A triangle is half its base times its height. A gable 30 feet wide and 8 feet tall adds 120 square feet. With two of them, the 1,440 becomes 1,680.

Split levels, hillside homes with a tall downhill side, and Spanish style homes with towers or parapets all take a little more care. Measure each wall section separately, multiply each by its own height, and add them up. On a hillside lot, the downhill wall can be much taller than the uphill one.

Windows, doors and what to leave in

For a quick estimate, many people leave windows and doors in. They are a modest share of most walls, and frames and sills still get attention during a wash. If you have a wall that is mostly glass, subtracting that area gives a closer number.

Decide which buildings to include. A detached garage, ADU or studio has its own walls. List them separately so the quote reflects what you actually want cleaned.

A worked example

Picture an L-shaped single story home. The long wing measures 50 by 25 feet and the short wing adds a 20 by 20 foot section. Walking the outside, the segments add up to 190 feet of perimeter. At 9 feet of wall height, that is 1,710 square feet.

Add one gable 25 feet wide and 6 feet tall, which is half of 150, or 75 square feet. The total is 1,785 square feet of wall. At the house washing rate of $0.35 per square foot as of October 2026, the estimate comes to $624.75. A detached garage measured the same way would be added as its own line.

Turning it into a price

Plug your number into the instant quote on this page. House washing on our calculator is $0.35 per square foot of exterior wall with a $195 visit minimum. The 1,680 square foot example above works out to $588.

Note anything unusual on your sketch, like walls that sit behind tall shrubs, upper walls over a steep slope, or areas behind locked gates. That helps the on-site confirmation go quickly.

Your estimate does not need to be perfect. Say Wash It confirms the flat price with you before work begins, so if the walls turn out a bit larger or smaller than you measured, you know the final number before anything starts.