By QuoteIron TeamUpdated 4 min read
Key takeaways
- Use area in square feet for sod, mulch, sealcoat, roofing and concrete. Use perimeter in linear feet for fence, edging and gutters.
- Roof area is the footprint times a pitch factor: about 1.12 at 6/12 and 1.20 at 8/12. The map does not show pitch, so confirm it on site.
- Pool water volume is surface area × average depth × 7.48 gallons per cubic foot.
Related: How to price jobs as a new solo tradesman · How to build a flat-rate price book · How to write a change order
What satellite measuring can and cannot tell you
Aerial imagery shows the outline of a lot, a roof and a pool from above. It does not show the slope of a roof, the height of a retaining wall, a buried line, or a fence that sits inside the property line. It also may not show a shed or deck built after the photo was taken, because imagery is often months or years old.
Use it to size a quote and set a range. Do not use it to order the exact amount of material.
The manual pin method
- Open the property on a satellite map and zoom until the shape fills about the middle third of the screen.
- Click each corner in order, going around the shape one way, and close the shape on your first point.
- Read the area and the perimeter the tool reports, and write both down.
- For an L-shaped yard, split it into two rectangles, measure each and add them. Subtract any area you will not work on, such as a house footprint or a pond.
- Check one dimension against something you know. A standard two-car garage door is 16 feet wide, and a standard parking space is about 18 feet long. If your pins are off by more than a few percent, redo them.
Area for materials, perimeter for edges
Sod, mulch, sealcoat, roofing and concrete are bought and priced by area, in square feet. Fence, edging, gutter, drip edge and border stone are priced by length, so you need the perimeter, in linear feet. The same shape gives you both numbers.
Example: a rectangular yard 60 feet by 120 feet is 7,200 square feet of area and 360 linear feet of perimeter.
Lawns: measure the grass you will actually cut
Start with the whole lot, then subtract everything that is not lawn: the house footprint, the driveway, patios, and beds you will not mow. Example: an 8,000 square foot lot with a 1,800 square foot house, a 600 square foot driveway and 300 square feet of beds has about 5,300 square feet of lawn. That is the number to quote for mowing or sod, not the lot size.
Roofs: the map shows the footprint, not the roof
From above, a roof looks smaller than it is, because a sloped surface covers more area than the footprint under it. Multiply the footprint by a pitch factor. The factor is the square root of one plus the rise over the run, squared. The common values are:
- 4/12 pitch: about 1.05
- 6/12 pitch: about 1.12
- 8/12 pitch: about 1.20
- 10/12 pitch: about 1.30
Then add a waste allowance. Many estimators add 10 to 15 percent for cuts and waste, and your supplier may want its own number. Example: a 1,600 square foot footprint at 6/12 is about 1,790 square feet of roof. Add 12 percent and you have about 2,000 square feet, or 20 roofing squares of 100 square feet each.
Pitch is the one number satellite imagery cannot show reliably. Confirm it on site, along with layers, valleys and penetrations such as vents and skylights, before you price a replacement.
Driveways, patios and concrete
For a rectangle, multiply length by width. For a curved or irregular slab, break it into rectangles and triangles and add them. Concrete is ordered by volume, so convert it: area times thickness in feet gives cubic feet, and dividing by 27 gives cubic yards.
Example: a 20 by 40 foot driveway poured 4 inches thick is 800 square feet times 0.33 feet, about 267 cubic feet, or about 10 cubic yards before waste.
Pools: area, average depth and gallons
A pool's surface area comes from the map, but the water volume needs depth. Use this:
Gallons = surface area (sq ft) × average depth (ft) × 7.48
The 7.48 is gallons per cubic foot. For a pool with a sloped floor, average depth is the shallow depth plus the deep depth, divided by two. Example: a 15 by 30 foot pool is 450 square feet. With a 3.5-foot shallow end and a 7.5-foot deep end, the average is 5.5 feet, so the volume is 450 × 5.5 × 7.48, about 18,500 gallons. A round pool uses its radius: pi times radius squared times depth gives cubic feet, which you then multiply by 7.48.
Depth is not on the map. Measure it or confirm it on site before you price chemicals or fill time.
When to confirm on site
- Any roof, before a replacement quote: pitch, layers, valleys and penetrations.
- Any slope, drainage problem or retaining wall that changes the work.
- Pools, for depth, equipment location and access.
- Lots with trees, overhangs or fences near the line, where the outline may not match the usable area.
- Buried utilities, sprinkler lines and septic areas before anyone digs.
- Anything the imagery is too old to show, such as a new shed, deck or addition.
- Any job where the number moves the price a lot. Set that threshold yourself.
The quote wording
Put the source of the number in writing so the customer knows what it is. Use a line like this in the scope or the notes:
Approx. 5,300 sq ft lawn, measured from aerial imagery; final scope confirmed on site.
The line does three jobs. It shows the area is approximate, it says where the number came from, and it makes the site visit part of the process rather than a surprise. If the site differs from the imagery, you can change the price with a reason on record.
QuoteIron has a built-in Measure for iPhone coming in 2.1.4.