Roof Pitch Chart

Roof pitch describes the steepness of a roof as a ratio of vertical rise to horizontal run. It is always expressed with 12 as the run — so a "6/12 pitch" means the roof rises 6 inches for every 12 inches (1 foot) of horizontal distance.

How Pitch Is Measured

Pitch is measured at the rafter or roof surface. Imagine a right triangle formed by:

• Run (base): The horizontal distance, always expressed as 12 inches
• Rise (height): The vertical distance the roof climbs over that 12 inches of run
• Rafter (hypotenuse): The actual surface length along the slope

Text-Based Diagram

        Ridge
         /|
        / |
       /  |  Rise (e.g., 6")
      /   |
     /    |
    /_____|
   Run (12")

  Pitch = Rise / Run = 6/12
  Angle = arctan(6/12) = 26.57°
  Multiplier = √(6² + 12²) / 12 = 1.118

Why the Multiplier Matters

When you measure a roof from overhead (satellite view or ground-level footprint), you get the flat, projected area. But the actual roof surface is larger because it slopes. The pitch multiplier converts flat area to true surface area. A steeper roof has a higher multiplier, meaning more materials are needed.

Slope Percentage

Slope percentage is another way to express steepness: (rise / run) × 100. A 6/12 pitch = 50% slope. This format is sometimes used in engineering and drainage specifications. A "2% slope" for flat roofs equals roughly 0.24/12 pitch — just enough for water drainage.

Our roof pitch chart above contains six columns of data for every pitch from 0.5/12 to 24/12. Here is what each column tells you and how to use it for your roofing project.

Pitch: Expressed as a ratio of rise over 12 inches of run. For example, "6/12" means the roof rises 6 inches for every 12 inches of horizontal distance. This is the standard way roofers communicate roof pitch in the United States.

Rise / Run: Shows the same information in inches. A 6/12 pitch has a rise of 6 inches over a run of 12 inches. This is what you physically measure with a level and tape measure on a rafter.

Multiplier: The pitch multiplier converts your flat footprint area to actual roof surface area. Multiply your footprint square footage by this number. For example, a 2,000 sq. ft. footprint at 6/12 pitch: 2,000 × 1.118 = 2,236 sq. ft. of actual roof area. This is the most important number for material ordering.

Angle: The pitch expressed in degrees, useful for engineering calculations and some building code references. A 6/12 pitch equals 26.57 degrees. Roofs above 45 degrees (12/12 pitch) require specialized installation methods.

Slope %: The rise divided by the run, expressed as a percentage. A 6/12 pitch equals 50% slope. This format is sometimes used in drainage engineering and on construction plans.

Category: A general classification of the roof pitch from "Flat / Low" through "Extreme" that helps you quickly identify which materials and installation methods apply to your roof.

Building codes and manufacturer specifications establish minimum roof pitch thresholds for every roofing material. Installing a material below its minimum pitch voids the warranty, violates code, and virtually guarantees water infiltration problems. Cross-reference this information with the pitch multiplier from our chart above when planning your project.

Asphalt shingles require a minimum 2/12 pitch per ASTM D3462 and most manufacturer installation guides. Between 2/12 and 4/12, special low-slope methods are mandatory: double underlayment, reduced shingle exposure, and enhanced sealing. Standard installation methods apply at 4/12 and above. The IRC Section R905.2.2 codifies these requirements.

Metal roofing offers the widest pitch range. Standing seam panels with mechanically seamed joints can be installed as low as 0.5/12 — nearly flat. Exposed-fastener metal panels require a minimum 3/12 pitch because the screw penetrations are more vulnerable to water at lower slopes. Per the Metal Construction Association guidelines, sealant at all laps is required below 3/12.

Clay and concrete tile require a minimum 2.5/12 pitch, though 4/12 is recommended. At pitches between 2.5/12 and 4/12, a fully waterproof underlayment system is essential because tile is not inherently waterproof — it relies on gravity and slope to shed water. The Tile Roofing Industry Alliance (TRI) technical manual provides detailed installation requirements by pitch range.

Slate requires a minimum 4/12 pitch per most manufacturer guidelines. Higher pitches (6/12 and above) extend slate's already extraordinary lifespan because steeper slopes reduce moisture exposure at the overlapping joints. The National Slate Association recommends increased headlap at pitches below 8/12.