Roof Pitch Calculator
Calculate your roof pitch ratio, angle in degrees, and slope percentage. Enter the vertical rise and horizontal run to get instant results for your roofing project.
What Is Roof Pitch?
Roof pitch is the measure of a roof's steepness, expressed as a ratio of vertical rise to horizontal run. In the United States, roof pitch is typically written as a ratio over 12 inches of horizontal distance. For example, a 4:12 pitch means the roof rises 4 inches for every 12 inches of horizontal run.
Understanding roof pitch is essential for choosing roofing materials, estimating material quantities, planning drainage, and ensuring your roof meets local building codes. Different pitches affect the amount of shingles, underlayment, and flashing you need for a roofing project.
Common Roof Pitches
Residential roofs in the US typically range from 4:12 to 9:12 in pitch. Here are the most common categories:
- Low Pitch (2:12 to 4:12): Often found on ranch-style homes and modern architecture. A 4:12 pitch is the most common standard residential roof pitch. These roofs are easier to walk on but may require special roofing materials for proper water shedding.
- Moderate Pitch (5:12 to 8:12): A 6:12 pitch is considered a moderate slope and is very popular for residential construction. These pitches provide excellent water drainage and a balanced aesthetic appearance.
- Steep Pitch (9:12 to 12:12): A 12:12 pitch creates a 45-degree angle and is considered steep. Steep roofs are common in areas with heavy snowfall as the angle helps snow slide off. They also create more attic space but require additional safety measures during installation.
How to Measure Roof Pitch
There are several methods to measure your roof's pitch:
- From the attic: Hold a level horizontally against a rafter. Measure 12 inches along the level, then measure the vertical distance from the end of the level to the rafter. This vertical measurement is your rise.
- From outside: Place a level against the roof surface at a convenient spot. Measure 12 inches along the level from where it contacts the roof, then measure straight down to the roof surface.
- Using a pitch gauge: A pitch gauge or digital angle finder can be placed directly on the roof to read the angle, which you can then convert to a pitch ratio.
Frequently Asked Questions
What is a 4/12 roof pitch?
A 4/12 roof pitch means the roof rises 4 inches for every 12 inches of horizontal run. This is one of the most common residential roof pitches and equals an angle of approximately 18.4 degrees. A 4/12 pitch provides adequate water drainage while remaining easy to walk on for maintenance. Most standard asphalt shingles can be installed on a 4/12 pitch or steeper without additional waterproofing measures.
How do I measure roof pitch?
To measure roof pitch, place a level horizontally against the roof surface and measure 12 inches along it. Then measure the vertical distance from the end of the level down to the roof surface. That vertical measurement is your rise, expressed as rise:12. For example, if you measure 6 inches of rise over 12 inches of run, your pitch is 6:12. You can also measure from inside the attic by holding a level against a rafter.
What roof pitch is considered walkable?
A roof pitch below 6:12 (approximately 26.6 degrees) is generally considered walkable for most people. Pitches between 6:12 and 8:12 require caution and possibly roof jacks for safe working. Any pitch above 8:12 is considered steep and typically requires specialized safety equipment such as harnesses, roof brackets, and toe boards. Always prioritize safety regardless of the pitch.
What is the minimum roof pitch for shingles?
The minimum roof pitch for standard asphalt shingles is typically 2:12, though many manufacturers recommend 4:12 or greater for optimal performance. For pitches between 2:12 and 4:12, you usually need to install a double layer of underlayment or an ice-and-water shield membrane beneath the shingles. Roofs with a pitch below 2:12 are considered flat and require different roofing materials like built-up roofing, modified bitumen, or single-ply membranes.