How do I calculate roof pitch from rise and run?

Divide the rise by the run and multiply by 12. For example, if your roof rises 8 feet over a 16-foot run: (8÷16)×12 = 6, giving you a 6:12 pitch. This means the roof rises 6 inches for every 12 inches of horizontal distance.

How do I convert roof pitch to degrees?

Use the arctangent function: Angle = arctan(pitch÷12). For a 6:12 pitch: arctan(6÷12) = arctan(0.5) = 26.57°. Common conversions: 4:12 = 18.43°, 6:12 = 26.57°, 8:12 = 33.69°, 12:12 = 45°.

What is a good roof pitch for my area?

For areas with heavy snow: 6:12 or steeper to shed snow. For heavy rain: 4:12 minimum. For hot, dry climates: 2:12 to 4:12 is acceptable. Standard residential is 4:12 to 9:12. Local building codes may specify minimum pitches.

How do I calculate rafter length from roof pitch?

Use the formula: Rafter Length = Run × √(1 + (Pitch/12)²). Or use Pythagorean theorem: Rafter = √(Rise² + Run²). For a 6:12 pitch with 12-foot run: √(6² + 12²) = √180 = 13.42 feet. Add overhang length for total rafter.

What's the difference between roof pitch and roof slope?

Roof pitch is expressed as a ratio (X:12), like 6:12. Roof slope is the same measurement expressed as a percentage or angle. A 6:12 pitch = 50% slope = 26.57°. All three describe the same roof steepness.

How do I measure roof pitch from the ground?

Use a pitch gauge app on your phone, or measure the roof visually by counting siding courses. For accuracy: Hold a level at the roof edge, mark 12 inches horizontal, measure vertical rise to the roof surface. This gives direct X:12 pitch.

What roof pitch requires walkable vs. steep roof safety?

Pitches up to 6:12 (26.57°) are generally walkable with caution. 7:12 to 9:12 requires roof jacks or toe boards. Above 9:12 (36.87°) requires scaffolding or harness systems. Always prioritize safety regardless of pitch.

How does roof pitch affect shingle requirements?

Steeper roofs need more shingles due to larger surface area. Calculate using: Roof Area = Footprint × Pitch Factor. Pitch factors: 4:12 = 1.054, 6:12 = 1.118, 8:12 = 1.202, 12:12 = 1.414. A 6:12 roof has 11.8% more area than flat.

Roof Pitch Calculator

Our Roof Pitch Calculator helps contractors, roofers, and DIYers determine roof slope in multiple formats. Calculate pitch as a ratio (e.g., 6:12), angle in degrees, slope percentage, and rafter length. Whether you're estimating materials, planning drainage, or building a new roof, this tool provides all the measurements you need for accurate construction.

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calendar_today Updated: April 2026

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New

roofing Roof Measurements

Calculate From

Rise

Run

Building Dimensions

Building Span

Eave Overhang

Roof Type

Roof Profile

analytics Results

Roof Pitch

6:12 pitch

26.57° • 50% slope

Angle

26.57°

Slope Percentage

50%

Rafter Length

13.42 ft (without overhang)

straighten

Total with overhang: 14.54 ft

Roof Area

644 ft²

Pitch factor: 1.118

Ridge Height

6 ft

Above wall plate

auto_awesome AI Analysis

Enter your values and calculate to receive AI-powered insights about your results.

roofing Pitch to Angle

2:12 9.46°

4:12 18.43°

6:12 26.57°

8:12 33.69°

10:12 39.81°

12:12 45.00°

home Pitch Categories

Flat 0-2:12

Low Slope 2-4:12

Conventional 4-9:12

Steep 9+:12

layers Material Min Pitch

Membrane 0:12

Metal 3:12

Asphalt Shingles 4:12

Clay Tiles 4:12

lightbulb Quick Tips

1 4:12 is minimum for standard asphalt shingles
2 Steeper roofs shed water and snow better
3 Use roof jacks for pitches above 6:12

How to Use This Calculator

Select Calculation Mode

Choose whether you know rise/run, pitch ratio, or angle

Enter Known Values

Input rise and run, pitch (X:12), or angle in degrees

Add Building Span

Enter total building width for rafter and area calculations

Optional: Add Overhang

Include eave overhang for total rafter length

Review Results

See pitch, angle, rafter length, and roof area

The Formula

Roof pitch is the ratio of vertical rise to horizontal run. A 6:12 pitch means the roof rises 6 inches for every 12 inches of horizontal run. The angle in degrees is calculated using arctangent. Rafter length uses the Pythagorean theorem.

Pitch = Rise ÷ Run, Angle = arctan(Rise ÷ Run), Rafter = √(Rise² + Run²)

lightbulb Variables Explained

Rise Vertical height of the roof (inches or feet)
Run Horizontal distance (half the span) (inches or feet)
Pitch Ratio expressed as X:12 (rise per 12 inches of run)
Angle Roof slope in degrees
Rafter Length of rafter from plate to ridge

tips_and_updates Pro Tips

Standard residential roofs range from 4:12 to 9:12 pitch - steeper slopes shed water and snow better

A 4:12 pitch (18.43°) is the minimum recommended for standard asphalt shingles

Measure rise and run in the same units (both inches or both feet) for accurate calculations

Low-slope roofs (below 3:12) require special roofing materials like rolled roofing or membrane

Steeper pitches (above 9:12) may require roof jacks or scaffolding for safe installation

When measuring existing roofs, use a 12-inch level and measure the rise at the 12-inch mark

Roof pitch describes the steepness of a roof as a ratio of rise to run. A 6:12 pitch means the roof rises 6 inches for every 12 inches of horizontal distance. Understanding pitch is essential for material selection, drainage planning, and structural design.

Low slope (1:12 to 3:12): Requires membrane roofing. Conventional (4:12 to 9:12): Standard for most homes, works with asphalt shingles. Steep slope (10:12+): Better snow shedding, more dramatic appearance, requires safety equipment for installation.

Different roofing materials have minimum pitch requirements. Asphalt shingles: 4:12 minimum (2:12 with special underlayment). Metal roofing: 3:12 minimum. Clay/concrete tiles: 4:12 minimum. Membrane/built-up: Works on flat to low slope.

Frequently Asked Questions

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