Roof Pitch
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Roof Pitch Calculator
Calculate pitch, slope percentage, roof angle, and rafter length from rise and run in seconds.
Fast roof math for builders & DIY projects
Roof Measurements
Construction Tool
Tip: Pitch is commonly expressed as rise over 12 inches of run, like 4/12 or 8/12.
Slope
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Percent grade
Rafter Length
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For entered run
Reference Span
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Comprehensive Guide to Roof Pitch
Roof pitch is the steepness of a roof, usually shown as rise over 12 inches of run. It matters for drainage, snow shedding, material selection, and the total amount of roofing surface required. A low-slope roof may be ideal for modern designs or certain membranes, while a steep roof often performs better in heavy rain or snow.
This calculator helps you turn basic measurements into useful project numbers fast. Enter the rise and run, then get the pitch ratio, angle in degrees, slope percentage, and rafter length without manual trigonometry.
Real-World Examples
A 4/12 roof is relatively gentle and common on suburban homes. A 12/12 roof is very steep and often found on cabins, historic homes, or designs that prioritize quick water runoff. Contractors use pitch to estimate materials, plan cuts, and match the roofing system to the structure.
Roof Pitch Reference Table
| Pitch | Angle | Notes |
|---|---|---|
| 2/12 | 9.5° | Very low slope; drainage details matter. |
| 4/12 | 18.4° | Common residential pitch. |
| 6/12 | 26.6° | Balanced look and water shedding. |
| 8/12 | 33.7° | Steeper roof with stronger visual profile. |
| 12/12 | 45.0° | Very steep; often used for dramatic designs. |
Frequently Asked Questions
How do I calculate roof pitch from rise and run?
Divide the rise by the run, then multiply by 12 to get the pitch ratio. The same ratio can also be converted into degrees with arctangent math.
What is the difference between pitch and slope?
Pitch is usually written as rise over 12 inches of run, while slope is the decimal or percentage version of that same relationship.
How do I estimate rafter length?
Use the Pythagorean theorem: rafter length equals the square root of rise squared plus run squared. This gives the diagonal roof length for the measured section.
Why does roof pitch matter?
It affects cost, drainage, material compatibility, and the amount of roof surface area needed for the job.
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