How do you calculate the pitch of a roof?

Roof pitch = Rise ÷ Run. Measure the vertical rise in inches over a 12-inch horizontal run. For example, if the roof rises 6 inches for every 12 inches of horizontal distance, the pitch is 6/12. Use our roof pitch calculator for instant results.

What is a good roof pitch?

Standard roof pitches range from 4/12 to 9/12. A 4/12 pitch is the minimum for standard shingles. 6/12 is the most common residential pitch. Steeper pitches (8/12+) shed water and snow better but cost more to build.

How do I calculate roof slope percentage?

Slope percentage = (Rise ÷ Run) × 100. A 6/12 pitch = (6÷12) × 100 = 50% slope. Our calculator converts between all formats: X/12 pitch, degrees, and percentage.

Roof Pitch Calculator - Calculate Slope, Angle & Rise

Calculate Roof Pitch

Enter rise and run to calculate the pitch ratio, angle in degrees, and slope percentage.

Rise (inches)

Run (inches)

Pitch Results

TIP: Standard roof pitch is expressed as rise/12. A 6/12 pitch means the roof rises 6 inches for every 12 inches of horizontal run.

Roof Pitch Converter

Convert between pitch ratio (X/12), degrees, and slope percentage.

Convert From

Pitch Value (X in X/12)

Conversion Results

Rafter Length from Pitch

Calculate rafter length based on roof pitch and building span.

Building Span (ft)

Roof Pitch

Overhang (inches)

Rafter Results

NOTE: Rafter length is the actual board length along the slope. Add extra for ridge cut and birdsmouth cut.

Roof Pitch Reference Table

Pitch	Degrees	Slope %	Multiplier	Description
1/12	4.8°	8.3%	1.003	Nearly flat, membrane roof
2/12	9.5°	16.7%	1.014	Low slope, rolled roofing
3/12	14.0°	25.0%	1.031	Minimum for shingles
4/12	18.4°	33.3%	1.054	Standard low pitch
5/12	22.6°	41.7%	1.083	Moderate pitch
6/12	26.6°	50.0%	1.118	Most common residential
7/12	30.3°	58.3%	1.158	Standard steep
8/12	33.7°	66.7%	1.202	Steep pitch
9/12	36.9°	75.0%	1.250	Very steep
10/12	39.8°	83.3%	1.302	Very steep, walkable limit
12/12	45.0°	100%	1.414	45° angle, steep

MULTIPLIER: Multiply the flat (plan) area of the roof by the pitch multiplier to get the actual roof surface area. Multiplier = √(1 + (pitch/12)²)

How to Calculate Roof Pitch

Understanding how to calculate roof pitch is essential for roofing projects, material estimation, and building code compliance. Roof pitch describes the steepness of your roof as a ratio of vertical rise to horizontal run.

Roof Pitch Formula

The basic roof pitch formula is: Pitch = Rise ÷ Run. In construction, pitch is expressed as "X/12" where X is the number of inches the roof rises per 12 inches of horizontal run. For example, a 6/12 pitch means the roof rises 6 inches for every 12 inches of horizontal distance.

How to Calculate Roof Pitch in Degrees

To convert roof pitch to degrees, use the formula: Angle = arctan(rise ÷ run) × (180 ÷ π). A 6/12 pitch equals 26.57°. Our roof pitch calculator performs this conversion instantly. Common conversions: 4/12 = 18.4°, 8/12 = 33.7°, 12/12 = 45°.

How to Calculate Roof Slope Percentage

Roof slope percentage = (Rise ÷ Run) × 100. A 6/12 pitch = 50% slope. This format is commonly used in engineering and drainage calculations. Our roof slope calculator converts between all three formats.

Measuring Roof Pitch

You can measure roof pitch from the attic using a level and tape measure. Place a level horizontally against a rafter, measure 12 inches along the level, then measure the vertical distance from that point to the rafter. That vertical measurement is your pitch per 12.

Frequently Asked Questions

How do you calculate pitch of a roof?+

Measure the rise (vertical height) and run (horizontal distance). Divide rise by run. In standard notation, measure how many inches the roof rises per 12 inches of horizontal run. A roof that rises 6 inches per 12 inches of run has a 6/12 pitch.

What is the most common roof pitch?+

6/12 (26.57°) is the most common residential roof pitch in the US. It provides a good balance of water shedding, attic space, and structural efficiency. Pitches between 4/12 and 9/12 are considered standard.

What is the minimum roof pitch for shingles?+

The minimum pitch for standard asphalt shingles is 2/12 to 4/12 depending on the manufacturer. Most manufacturers require at least 4/12 for standard installation. Below 2/12, a membrane or built-up roof system is recommended.

How do I convert roof pitch to degrees?+

Use the formula: degrees = arctan(pitch/12) × (180/π). Quick conversions: 3/12 = 14°, 4/12 = 18.4°, 6/12 = 26.6°, 8/12 = 33.7°, 10/12 = 39.8°, 12/12 = 45°. Our converter does this instantly.

How do I calculate rafter length from roof pitch?+

Rafter length = √(run² + rise²) + overhang. For a 24-foot span at 6/12 pitch: run = 12ft, rise = 6ft, rafter = √(144+36) = 13.4ft + overhang. Our rafter calculator computes this automatically.