Roof Pitch Calculator

Roof pitch in 30 seconds

Roof pitch is how steep a roof is, written as rise over run. A 6/12 pitch means the roof goes up 6 inches for every 12 inches of horizontal run. Run is always 12 in standard notation, so the only number that changes is the rise. The calculator above takes your rise and run and gives you the pitch ratio, the angle in degrees, and the area multiplier you need to order shingles.

What is roof pitch?

Roof pitch (sometimes called slope) is the steepness of a roof expressed as a ratio. The first number is rise — how far the roof climbs vertically. The second number is run — the horizontal distance, which in roofing is almost always 12 inches. A 4/12 roof rises 4 inches over 12 inches of run. A 12/12 rises 12 inches over 12 inches, which is a 45-degree angle. Most residential roofs in the US fall between 4/12 and 9/12. Knowing your pitch is the first step to ordering materials, estimating labor, and deciding what kind of fall protection a job needs.

Roof pitch to degrees conversion table

Plans, building inspectors, and engineers sometimes specify roof angle in degrees instead of pitch. The conversion is the inverse tangent of rise/run, but most contractors just memorize the common ones or look them up. Here is the full table covering every standard residential and commercial pitch.

Use the calculator above for any pitch not on this list — it handles fractional pitches and degree-to-pitch conversion both directions.

How to measure roof pitch (3 ways)

There are three reliable ways to measure pitch. The right one depends on whether you can safely access the roof or attic.

• From the attic (most accurate). Press a 2-foot level horizontally against the underside of a rafter. From the 12-inch mark on the level, measure straight up to the rafter. That number is your rise per 12 inches of run, which is the pitch.
• From the ground with a speed square. Hold a speed square at arm's length so the level edge sits on the gutter line. Sight up the rake of the roof and read the angle in degrees from the square's pivot. Convert with the table above.
• On the roof. Lay a 2-foot level on the shingles parallel to the slope. Hold a tape on the high end of the level and measure straight down to the roof surface. Multiply that number by 6 to get rise per 12 inches.

Modern phone apps with a built-in level work too, but always confirm with one of the methods above before ordering thousands of dollars of materials.

What is the roof pitch multiplier and why does it matter?

The pitch multiplier — sometimes called the slope factor — converts the footprint area (the shadow the roof would cast on the ground) into the actual sloped surface area you need to cover with material. A 1,000 sq ft footprint at 6/12 pitch is really 1,118 sq ft of roof, because 1,000 × 1.118 = 1,118. Skip the multiplier and you'll come up short on shingles, underlayment, ice and water shield, and ridge cap — every single time. The calculator above shows the multiplier alongside the pitch, so you can plug it straight into your material takeoff.

What does each pitch range look like in practice?

Different pitch ranges get treated differently in code, materials, and labor. Here's how each one plays out on a real job.

• Flat to 2/12 — Membrane only. EPDM, TPO, modified bitumen. No shingles. Drains slowly so flashing details matter.
• 2/12 to 4/12 — Low slope. Standing seam metal works well. Asphalt shingles need a double layer of underlayment to meet code.
• 4/12 to 9/12 — The sweet spot. Standard shingles, standard labor, walkable without staging. About 80% of US homes.
• 9/12 to 12/12 — Steep. Production slows about 25–40%. Roof jacks and toe boards are required for safety.
• Over 12/12 — Very steep. Scaffolding or a harness system required. Labor cost can double per square versus a 6/12.

How pitch affects material costs and labor

Steeper roofs cost more for two reasons. First, more square footage. A 12/12 covers 41% more area than the same footprint at flat. That's 41% more shingles, underlayment, fasteners, and ridge cap. Second, productivity drops as pitch climbs. Crews work slower and need more safety equipment. Most estimators use a labor pitch factor: 1.0 up to 6/12, 1.25 at 7/12 to 9/12, 1.5 at 10/12 to 12/12, and 2.0 or higher above that. When you bid a steep job at the same labor rate as a 6/12, you'll lose money every time.

Rise over run explained

Rise is how much the roof goes up vertically. Run is how far it goes horizontally. By convention, the run in pitch notation is always 12 inches — so a 6/12 pitch means 6 inches of rise per 12 inches of run. Some old plans use a 1-foot run instead, but the math is the same. Rise/run also gives you the tangent of the roof angle, which is why arctan(rise/12) returns the angle in degrees.