Roof Square Footage Calculator

Measure the roof's flat footprint from above, then multiply by a pitch factor to account for the slope. The footprint is what you see looking straight down; the actual roof surface is larger because it rises. The standard factor is √(1 + (rise/12)²) — a 6-in-12 roof is ×1.118, an 8-in-12 is ×1.202. So a 1,640 sq ft footprint on a standard-pitch roof is about 1,837 sq ft of roof surface. SurfaceMeasure traces the footprint from satellite imagery and applies the pitch factor for you.

It's an approximation, and it's the same approximation every roof cleaning calculator uses — but it starts from a better number. Competing calculators ask you to estimate the footprint from your home's living area and then add 20–30% for pitch, which stacks two guesses. Tracing the roofline removes the first guess entirely: the footprint is measured, not estimated, and satellite imagery shows the eave edge, so overhangs are already included. What remains is the pitch factor, which is exact geometry once you know the pitch. Pick the tier and you're typically within a few percent — plenty for a soft-wash quote.

No. This is built for cleaning and soft-wash quoting, where a few percent either way doesn't change the job. Re-roofing needs more precision than a pitch tier can give: material ordering has to account for the exact pitch, waste factor, hips and valleys, ridge and starter courses, penetrations, and multiple roof planes at different slopes. Use a roofing takeoff tool or measure on site for that work. If you're bidding a wash, this is the right tool; if you're bidding a tear-off, it isn't.

Not an asphalt shingle roof. High pressure strips the granules that protect the shingle, shortens its life, and voids most manufacturer warranties — it's one of the fastest ways for a new operator to turn a $400 job into a claim. Asphalt, tile, and cedar get soft washed: low pressure and a cleaning solution that does the work chemically. Metal roofs are the exception and can take moderate pressure. Measuring the roof is the same either way; what changes is the method and the rate.

Soft washing typically runs about $0.15–$0.60 per square foot, with the spread driven by roof height, pitch, access, and how much organic growth is on it. Pressure washing — metal roofs only — runs roughly $0.20–$0.70. Moss removal is the most labor-intensive at roughly $0.20–$0.75 because it often needs manual work before and after the chemical. On a typical 1,800 sq ft roof surface that puts a straightforward soft wash somewhere around $270–$1,080 before any minimum or height premium.

They're already in there when you trace from satellite, which is a real advantage of this method. Looking straight down, what you see is the roof edge — the eave — not the wall line beneath it. So the traced footprint includes the overhang automatically. Methods that start from a home's living area miss this and have to guess a percentage to add it back.

Trace each section as its own shape and apply the tier that matches it, then add the results. A main roof at 6-in-12 with a lower porch roof at 3-in-12 should be measured as two numbers, not averaged into one. The calculator on this page takes multiple sections, and in the app each traced shape keeps its own area so you can apply a different factor to each.

Partly, and this is the main limitation. Roofs are the most visible surface on a property from above — nothing obstructs them except vegetation — but a heavily canopied roof will have edges you can't follow confidently. Trace the portion you can see, use the visible ridge and eave lines to infer the rest, and confirm the dimensions on site if the tree cover is severe. Most roofs trace cleanly.