Driving out to measure every lead costs fuel and a morning, and many of those leads never book. A satellite outline gets you a defensible number in a few minutes. The catch is that a map shows a flat, top-down view - so roofs, lawns and walls each need one extra step to turn the drawn outline into the area you actually work on.
Roofs: multiply the footprint by a pitch factor
Outline each roof plane on the map. What you get is the footprint - the area the roof covers seen from above. A sloped roof has more real surface than its footprint, and the steeper the slope, the bigger the difference. Multiply by the pitch factor:
| Pitch (rise / 12 in run) | Pitch factor | 1,500 sq ft footprint becomes |
|---|---|---|
| Flat | 1.000 | 1,500 sq ft |
| 4/12 (low) | 1.054 | 1,581 sq ft |
| 6/12 (medium) | 1.118 | 1,677 sq ft |
| 8/12 (steep) | 1.202 | 1,803 sq ft |
| 12/12 (very steep) | 1.414 | 2,121 sq ft |
The factor is the square root of 1 + (rise/12) squared - the length of the sloped surface compared with its flat run. If you do not know the pitch, count the courses of shingles in a street-view image or ask the customer for a photo of the gable end; most homes fall between 4/12 and 8/12.
Lawns: draw the lot, then cut out what is not grass
Draw the outer boundary of the treatable area first. Then draw the house, driveway, patio, pool and large beds as separate shapes and subtract them. What is left is the net turf area you will actually mow, treat or seed.
| Shape | Area |
|---|---|
| Lot boundary | 10,000 sq ft |
| House footprint (cutout) | - 2,200 sq ft |
| Driveway (cutout) | - 600 sq ft |
| Pool and deck (cutout) | - 450 sq ft |
| Net turf area | 6,750 sq ft |
Siding and house washing: perimeter x wall height
Walls do not show up on a satellite image at all, so measure them indirectly. Trace the house perimeter as a line to get linear feet, then multiply by the wall height. A common rule of thumb is about 10 feet per story; adjust for tall ceilings, gables and walk-out basements.
Example: a 160 ft perimeter on a two-story home is 160 x 20 = 3,200 sq ft of wall. Subtracting windows is optional - most washers leave them in, because working around them takes time too.
Hardscape: measure every surface separately
Driveways, walkways and patios often get different treatment (sealing, stain removal, different surface cleaners). Draw each one as its own shape and tag it, so the estimate can show a line per surface instead of one lump sum.
Getting accurate numbers
- Zoom in fully and place points on the edge of the surface, not the shadow beside it.
- Trees hide edges - follow the visible line and close the shape where the edge must be.
- Satellite imagery can be months or years old. Ask for a photo if the property may have changed.
- Round in your favour only through pricing rules (minimums, condition), never by padding the measurement - customers can measure too.