Roof Pitch Calculator
Calculate roof pitch, angle, and slope from rise and run measurements.
Run is usually 12 inches. Change it only if measuring a custom span.
This tool is for informational and educational purposes only. It is not a substitute for professional financial, medical, legal, or engineering advice. See Terms of Service.
Can't find what you need?
Request a ToolHow to Use the Roof Pitch Calculator
This calculator converts rise and run measurements into pitch ratio, angle in degrees, slope percentage, and pitch factor. Here is how to use it:
- Enter the rise. Rise is the vertical height gained over a horizontal distance. For standard pitch measurement, this is the number of inches the roof rises for every 12 inches of run. A 6-in-12 pitch means the roof rises 6 inches over 12 inches of run.
- Enter the run. The run defaults to 12 inches because roof pitch is conventionally expressed per 12 inches of run. If you measured a different span, enter the actual horizontal run in inches and the calculator will normalize the result to the standard X/12 format.
- Read your results. The pitch ratio (e.g., 6/12) is the primary result. Below it you will see the equivalent angle in degrees, the slope as a percentage, the pitch factor for area calculations, and the pitch category.
Results update instantly as you type. Use the Share button to send your inputs to a contractor or roofing supplier, or Copy to paste the ratio into a document.
About Roof Pitch
Roof pitch describes how steeply a roof rises relative to its horizontal run. In the United States the standard expression is a fraction over 12: a 4/12 pitch rises 4 inches for every 12 inches of horizontal run. This same pitch can also be expressed as an angle (18.4 degrees) or a slope percentage (33.3%).
The pitch factor is used to convert a building's footprint area to its actual roof surface area. Multiply the horizontal floor area by the pitch factor to get the true roof area for ordering shingles, underlayment, or metal panels. A 6/12 pitch has a factor of approximately 1.118, meaning a 1,000 sq ft footprint requires about 1,118 sq ft of roofing material.
Pitch also determines what roofing products are appropriate. Low-slope roofs (under 4/12) require special low-slope shingles, EPDM, TPO, or built-up roofing. Conventional slopes (4/12 to 8/12) work with all standard shingle types. Steep roofs (9/12 and above) may need additional fasteners and special installation techniques.
Frequently Asked Questions
What is a standard roof pitch for a residential home?
The most common residential roof pitches in the United States are 4/12, 5/12, and 6/12. A 4/12 pitch (18.4 degrees) is the minimum recommended for standard asphalt shingles and sheds water reliably without being too steep to walk safely. A 6/12 pitch (26.6 degrees) is considered a steep but walkable conventional slope. Pitches of 8/12 and above are considered steep and require extra safety precautions during installation.
How do I measure roof pitch from the ground?
The most common method is to use a level and a tape measure from the attic or on the roof. Hold a 12-inch level horizontally against the rafter or roof deck, then measure straight down from the 12-inch mark to the roof surface. That vertical measurement in inches is your rise. For example, if you measure 5 inches down, your pitch is 5/12. You can also use a digital angle finder or a smartphone inclinometer app placed flat on the roof surface, then convert the angle to a pitch ratio using this calculator.
What is pitch factor and why does it matter for roofing?
Pitch factor (also called roof multiplier or slope factor) accounts for the fact that a sloped roof covers more actual surface area than the flat footprint below it. It is calculated as the square root of (1 + (rise/run)^2). A flat roof has a pitch factor of 1.000, meaning the roof area equals the floor area. A 6/12 pitch has a factor of about 1.118, so a house with a 1,500 sq ft footprint would have roughly 1,677 sq ft of actual roof surface. Always use the pitch factor when ordering roofing materials to avoid running short.
What roof pitch is too steep to walk on safely?
Most roofing professionals consider anything above 7/12 (30.3 degrees) too steep to walk on without additional safety equipment such as roof jacks, scaffolding, or a safety harness. A 6/12 pitch is generally considered the upper limit of comfortable walking with proper non-slip footwear. Below 4/12, the roof is easy to walk on but may not shed water quickly enough for standard shingles, requiring a low-slope roofing product. Always use appropriate fall protection regardless of pitch when working at height.