How to Measure a Roofline for Christmas Lights From a Photo

You can get a quotable roofline measurement from one photo in about two minutes. The method is the same whether you use a piece of paper or the free GlowBid tool: pick something in the photo with a known length, set the scale from it, trace each run, and add the jumps and peaks. In 2026 we quote roughly nine out of ten houses this way and confirm on site the day of the install.

What you need

• One photo of the front of the house, taken square-on from across the street, in daylight. The whole roofline should be in frame.
• One known length in the same photo. The garage door is ideal: 8 ft for a single, 16 ft for a double. A front door is 36 in. A standard window is often 36 in wide, but check.
• Your per-foot rate card, so the footage turns into a price while the homeowner is still on the phone.

Step 1: set the scale

Find the reference object and mark both ends. If the door is 16 ft and it spans 320 pixels in the photo, every foot is 20 pixels. That scale is only true for surfaces in the same plane as the door: the front face of the house. Keep that in mind for step 4.

Step 2: trace the runs

Trace each run type separately, because they price separately:

Run	What it is	How installers usually price it
Roofline	Eaves, the long horizontal runs along the gutter line	Per foot, the base rate
Ridge line	The top edge of a gable, if you light it	Per foot, often the same rate as roofline
Peak	The two sloped edges of a gable	Per foot plus a steep-pitch premium
Jump	Unlit cord between two lit runs	Reduced per-foot rate or flat per jump
Ground and trees	Walkway strands, tree wrap	Per foot, or per tree for wraps

Tap or click along the eave, corner to corner. A bungalow front elevation is usually 40 to 60 ft of roofline; a two-storey with a garage bump-out often runs 90 to 130 ft once you include the returns.

Step 3: add jumps and peaks

Every gable has two sloped edges and usually a jump at the bottom to get back to the eave. Count them. On a typical two-gable front you will have four peak runs and two or three jumps. Peaks are where installers lose money: the pitch makes them slower and more dangerous, so give them their own rate.

Step 4: know which numbers to trust

A run that lies in the same plane as your reference reads true. A run that angles away from the camera, like a side eave or a return, reads short, sometimes by a third. Mark those runs and type the real length from a tape, a laser, or the county's building footprint. GlowBid flags them automatically as "may be short" and lets you type the true length; on paper, write a question mark next to them.

Then add a materials buffer. Ten percent is common. The buffer goes on the order, not on the price, and the quote says plainly that the measurement is photo-based and confirmed on site. Homeowners accept that; they do not accept a surprise on install day.

Step 5: turn footage into a quote

Multiply each run by its rate, add the peak premium, the jumps, the controller and any add-ons, then check it against your minimum job. For a 112 ft roofline at $25 per foot with two peaks (36 ft at $28) and two jumps (14 ft at $12), the lighting comes to $2,800 plus $1,008 plus $168, before the controller. GlowBid does this arithmetic from the drawing, so the drawn line, the footage and the price are one object and cannot disagree.

Common mistakes

• Measuring from a photo taken at an angle. Stand across the street, centred on the house.
• Using a window as the reference without checking its real width. Windows vary; garage doors do not.
• Forgetting the returns. The short pieces that wrap around a corner add up on a two-storey.
• Skipping the buffer and running out of track on the last run.
• Tracing satellite or Street View images. Old imagery, and against Google's terms.