How to measure a roof with Google Maps: the measure-distance tool, step by step

Google Maps measures a roof with one right-click: choose Measure distance on the first corner, click your way around the drip edge, and close the shape to read the perimeter and the footprint area in feet and metres. That is the whole tool. It knows nothing about pitch, so the area it prints is the footprint, and every sloped length still needs a factor before it goes on an order. Here is the routine, a worked gable roof, and where Google Maps stops being enough.

Before you click: satellite view, straight down, zoomed in#

• Type the address, open Layers in the bottom-left corner and pick the Satellite view. The default map's building outlines can lag the roof by years.
• Zoom until the roof fills the window. At neighbourhood zoom one pixel is a foot or more, and every corner you click is off by a pixel or two.
• If the houses stand up and the view tilts, open Layers, then More, and switch off Globe view. The tool draws on the flat map, and a leaning roof puts your points on a wall.

This is the Google Maps version of the general method in how to measure a roof from satellite imagery: trace the outline, set the pitch, label the edges, add waste. Google Maps covers the first step only. Google Earth does a little more, with a polygon tool and a historical slider; that version is in how to measure a roof on Google Earth.

The measure-distance tool, step by step#

1. Right-click the first eave corner and choose Measure distance. A white dot appears.
2. Click the next corner. A line draws, and a label at the new point shows the running total.
3. Continue around the drip edge, one corner per click. Each label is the total so far; subtract the previous label to get that edge.
4. Click your starting dot to close the shape. The card at the bottom now shows total distance, the perimeter, and total area, the footprint, in feet and in metres.
5. Drag a dot to correct it; click a dot to delete it. Right-click and choose Clear measurement to start over.
6. Write every edge down with what it is, eave, rake, eave, rake, before you close the card. Google Maps keeps nothing.

Ridges, hips and valleys sit inside the outline, so measure each as its own run, end to end, then clear and move on. On the phone app, long-press a corner to drop a pin, swipe up, tap Measure distance, then drag the crosshair to each corner and tap Add point; it totals distance only. Use the phone for a drive-by check and the desktop for the number you order to.

What the numbers mean#

Pitch factors: 4/12 is 1.054, 6/12 is 1.118, 7/12 is 1.158, 8/12 is 1.202, 12/12 is 1.414. Hip and valley factors run lower, 1.061 at 6/12 and 1.106 at 8/12; the full tables and formulas are in how to calculate roof pitch. The pitch itself comes from somewhere else: a gable-end photo, the attic, or dropping the pegman onto the street to look at the rake, covered in finding roof pitch from Street View.

A worked gable roof#

A plain gable, 48 by 28 feet at the drip edge, ridge along the long side, 7/12 confirmed from the gable end in Street View. Google Maps, closed shape: total distance 152 feet, total area 1,344 square feet.

• Roof area: 1,344 × 1.158 = 1,556 square feet, or 15.6 squares. With 10% waste, 17.1 squares, so 52 bundles at three per square.
• Eaves: two runs of 48 feet, 96 feet. Level, so drip edge and starter are ordered to it.
• Rakes: the map shows four runs of 14 feet, half the span. Times 1.158 is 16.2 feet each, 64.8 feet in all. Drip edge for the rakes is 65 feet, not 56.
• Ridge: 48 feet, level, one run end to end. That is the ridge cap length.
• Check: 96 + 56 = 152 feet matches the card. The 152 is not your drip-edge total; 96 + 65 = 161 feet is.

Google Maps supplied two numbers, 152 and 1,344. Everything the supplier needs came from the pitch and the geometry.

Where you trip#

• Clicking the wall line. The shadow under the overhang reads as the edge. A one-foot overhang on that 48 by 28 house is 148 square feet of footprint, about 1.7 squares after the pitch factor, missing from the order.
• Reading total area as roof area. The card says 1,344, the roof is 1,556. The gap is the pitch, and it grows with the slope: 5% at 4/12, 41% at 12/12.
• Taking the closed-shape perimeter as drip edge. Right on a hip roof, where the whole outline is eave. Wrong on a gable roof, where the rakes sit in it at map length.
• One shape, one pitch on a cut-up roof. A 3/12 porch under an 8/12 main gets its own shape and its own factor; one factor over both is wrong on both.
• An old capture. Google Maps has no date slider. An addition or a tree grown over a valley is invisible if the capture predates it.

When Google Maps is enough, and when to switch#

It is enough for a ballpark before the first visit, for confirming the footprint on a report you ordered, and for settling a "how big is that roof" phone call in minutes. It is not enough for an order you sign, because the pitch, the edge types and the arithmetic live in your notebook and nothing checks them.

A roof measurement tool does the same trace with the geometry attached: trace the outline over satellite imagery or your own drone or phone photo, set a pitch per facet, label each edge once, and the roof area, squares and line totals come out computed, exported as a PDF for the supplier. RoofStruct's measuring builder works this way, and self-serve measuring and PDF reports are free and unlimited, no card needed. Use Google Maps for the look; measure the job in a tool that knows a rake from an eave.

FAQ#

Does Google Maps measure roof area?#

It measures footprint area. Close the shape on the desktop site and the card prints the total area of the flat outline. Multiply by the pitch factor for the roof's slope to get roof area; a 6/12 roof is 1.118 times its footprint.

Can Google Maps measure roof pitch?#

No. The measure tool works on the flat map and has no slope in it. Get the pitch from a gable-end photo, the attic or Street View, and apply it to the footprint and to the rakes, hips and valleys yourself.