📐 Roof Pitch Calculator
Enter a roof's rise and run to get its slope angle in degrees, the slope factor for surface area, and the standard rise-per-12 pitch ratio.
🔧 Find Your Roof's Pitch
What is a Roof Pitch Calculator?
A roof pitch calculator translates a roof's rise and run into the three numbers builders rely on: the pitch ratio written on drawings, the slope angle in degrees, and the slope factor used to convert footprint area into true sloped area for ordering materials.
Whether you are designing a new roof or quantifying shingles for a re-roof, these figures keep your estimates honest. Use them for planning, and verify the structure with an engineer.
❓ Frequently Asked Questions
What does roof pitch mean?
Pitch describes how steep a roof is, expressed as the vertical rise over a horizontal run — conventionally per 12 inches. A 6:12 roof climbs 6 inches for every 12 inches of horizontal travel. The calculator takes your rise and run and reports the equivalent pitch per 12 along with the slope angle in degrees.
What is the slope factor and why does it matter?
The slope factor is the ratio of the sloped roof length to its horizontal run, found with the Pythagorean theorem. Multiply a roof's plan (footprint) area by this factor to get the true sloped surface area — the figure you need when ordering shingles, underlayment, and sheathing, since a steeper roof has more material than its footprint suggests.
How does pitch affect roofing material choice?
Low-slope roofs shed water slowly and usually need membrane or standing-seam systems, while steeper pitches drain fast and suit shingles, tile, or slate. Pitch also affects wind uplift, snow load, and walkability. Knowing the angle early helps you pick a code-compliant material and the right installation details.
Is this calculator a substitute for a structural design?
No. It gives accurate geometry — angle, slope factor, and ratio — but it does not size rafters or assess loads. Snow, wind, and dead loads must be checked against local code. Use these figures for planning and quantity take-offs, and verify the structure with a qualified engineer.