Figure Roof Pitch from Rise and Run
Enter your roof rise and run in the same unit (inches, feet, centimeters, etc.). The calculator returns pitch, angle, slope %, and rafter length.
Convert Known Pitch (X-in-12) to Rise
Use this helper when you already know the pitch format, such as 4-in-12 or 9-in-12.
If you're trying to figure roof pitch quickly, this page gives you both a practical calculator and a plain-English guide. Whether you're planning shingles, framing a shed, checking an existing roof, or estimating materials, understanding pitch is one of the first steps.
What roof pitch means
Roof pitch describes how steep a roof is. In residential construction, pitch is usually written as X-in-12, where X is the number of inches the roof rises for every 12 inches of horizontal run.
- 4-in-12 means the roof rises 4 inches for each 12 inches of run.
- 6-in-12 is steeper than 4-in-12.
- 12-in-12 is a 45° angle.
The calculator above computes this automatically from rise and run so you do not need to do trigonometry by hand.
Formulas used in this roof pitch calculator
1) Pitch in 12 format
Pitch (X-in-12) = (Rise ÷ Run) × 12
2) Roof angle in degrees
Angle = arctangent(Rise ÷ Run)
3) Slope as a percentage
Slope % = (Rise ÷ Run) × 100
4) Rafter length for entered run
Rafter = √(Run² + Rise²)
This is the Pythagorean theorem and is useful when planning framing members, cuts, and material ordering.
How to use the calculator correctly
- Measure the horizontal run and vertical rise.
- Use the same unit for both values (all inches, all feet, etc.).
- Click Calculate Pitch.
- Review pitch, angle, slope %, and rafter length in the result panel.
Common roof pitch ranges and what they imply
Low-slope roofs (typically below ~3:12)
- Need materials designed for low-slope conditions.
- Drainage details are more critical.
- Often used in modern or commercial styles.
Conventional residential pitches (~4:12 to 9:12)
- Common for asphalt shingles and many neighborhoods.
- Balanced look and generally good water shedding.
- Safer and easier to work on than very steep roofs.
Steep roofs (10:12 and above)
- Move water and snow quickly.
- Create dramatic curb appeal and more attic volume.
- Increase labor complexity, safety needs, and cost.
Practical example: figure roof pitch from field measurements
Suppose you measure:
- Run = 12
- Rise = 7
The roof pitch is (7/12) × 12 = 7-in-12. The angle is about 30.26°. The slope is roughly 58.33%. That places it in a moderately steep residential range.
Where mistakes happen (and how to avoid them)
Mixing units
If run is in feet and rise is in inches, your result will be wrong. Convert first so both inputs match.
Confusing span and run
Run is horizontal distance from wall to ridge on one side (for symmetric gables), usually half of span.
Estimating by eye
A visual guess can easily miss by several degrees. That small error can affect shingle suitability, flashing details, and material quantity.
Why pitch matters for design and cost
- Materials: Some roofing products have minimum slope requirements.
- Water management: Pitch influences drainage speed and standing-water risk.
- Labor: Steeper roofs generally increase setup time and safety equipment needs.
- Aesthetics: Pitch changes the architectural character of the entire home.
- Volume: Higher pitch can create more attic or vaulted ceiling space.
Quick FAQ
Is pitch the same as angle?
Not exactly. Pitch is usually expressed as X-in-12. Angle is measured in degrees. They describe the same slope in different formats.
What is a 12/12 roof?
A 12-in-12 roof rises 12 units for every 12 units of run, which equals a 45° angle.
Can I use metric units?
Yes. Just keep run and rise in the same unit and the math still works.
Do I need code checks?
Yes. Always verify local building code requirements, product installation specs, load conditions, and permit rules before construction.
Bottom line
When you need to figure roof pitch fast, measuring rise and run is the simplest path. Use the calculator to get pitch, angle, slope percentage, and rafter length in seconds. Then validate your design choices with local code and manufacturer instructions before building.