Convert roof pitch to degrees, get your solar suitability rating, and calculate optimal panel tilt in seconds. Works with rise:run ratios, degrees, and percent slope — no sign-up required.
Roof pitch is one of the most critical site assessment factors for solar installations. It affects racking system selection, structural load calculations, panel tilt optimization, and potential energy yield. Yet most solar professionals still have to manually look up conversion tables or use a separate pitch measurement app.
Our Roof Pitch Calculator converts any roof pitch format — rise:run ratio (like 6:12), degree angle, or percent slope — into all three representations instantly. It also gives you a solar suitability rating, the optimal panel tilt deviation from the roof angle, and an estimated production impact.
Built for solar installers and designers, this tool gives you everything you need to make roof pitch decisions during a site walk — directly in your browser.
Multi-Format Conversion
Enter pitch as rise:run (e.g. 6:12), degrees (e.g. 26.6°), or percent slope (e.g. 50%). Get all three formats instantly.
Solar Suitability Rating
Get an immediate suitability assessment: Excellent, Good, Marginal, or Not Recommended — with the specific reasons why.
Visual Pitch Diagram
See a dynamic visual representation of your roof pitch with angle markers and recommended panel tilt overlay.
Site Surveys
Quickly enter the measured pitch from your inclinometer to get degrees, percent slope, and a solar suitability rating all at once.
Racking System Selection
Different racking systems have pitch range requirements. Confirm your chosen pitch falls within the racking manufacturer's spec.
Production Estimates
Pitch affects panel tilt angle and annual energy yield. Use the tilt deviation output to apply a production adjustment factor in your energy model.
Select Your Input Format
Choose whether you'll enter pitch as a rise:run ratio (most common in the U.S.), in degrees, or as a percent slope.
Enter Your Pitch Value
Type in your measurement. For rise:run, enter both values (e.g., rise = 6, run = 12). For degrees or percent, enter the single value.
Select Your Location
Choose your state or latitude zone to enable the optimal tilt angle calculation and production impact estimate.
Review All Three Formats
The calculator instantly shows your pitch in rise:run, degrees, and percent slope — no manual conversion needed.
Check Solar Suitability
Review your suitability rating and the specific notes about your pitch — self-cleaning threshold, walkability, and racking compatibility.
Pitch in Degrees
e.g. 26.6°
Angle from horizontal used by structural engineers and solar energy models. 6:12 pitch = 26.6°.
Rise:Run Ratio
e.g. 6:12
Standard U.S. roofing notation: vertical rise per 12 inches of horizontal run.
Percent Slope
e.g. 50%
Rise divided by run as a percentage. Used in civil engineering and European standards.
Solar Suitability
e.g. Excellent
Rating based on self-cleaning angle (15°+), walkability, and racking compatibility.
Tilt Deviation
e.g. 8.4°
Difference from optimal tilt for your latitude. Each 5° deviation ~1–3% production impact.
Rise:Run to Degrees
Degrees = arctan(rise ÷ run)
Degrees to Rise:Run
Rise = round(tan(degrees) × 12, 1) Run = 12
Percent Slope
Percent Slope = (rise ÷ run) × 100
Optimal Tilt Angle (NREL Regression)
Optimal Tilt = 0.76 × latitude + 3.1°
Tilt Deviation
Deviation = |roof angle° − optimal tilt°|
Solar suitability thresholds based on: 14.5° self-cleaning threshold (dust/pollen), standard racking weight limits, and installer safety standards for rooftop access.
Worked example: A roof with 6-inch rise over 12-inch run = 6:12 pitch. Tilt angle: arctan(6/12) = 26.6°. Optimal solar tilt for Los Angeles (33°N) = 0.76 × 33 + 3.1 = 28.2°. Tilt deviation = |26.6° − 28.2°| = 1.6° — excellent match. A 4:12 pitch (18.4°) produces approximately 95% of optimal annual yield. A 12:12 pitch (45°) produces approximately 92% of optimal yield in most US locations.
Calculations sourced from SurgePV’s Roof Pitch Calculator — surgepv.com/tools/roof-pitch-calculator/
Common U.S. roof pitches with solar suitability ratings. Use the calculator above for your exact pitch.
| Pitch (Rise:Run) | Degrees | % Slope | Solar Suitability | Notes |
|---|---|---|---|---|
| 1:12 | 4.8° | 8.3% | Not Recommended | Pooling risk, no self-cleaning |
| 2:12 | 9.5° | 16.7% | Marginal | Low self-cleaning, flat racking may be needed |
| 3:12 | 14.0° | 25.0% | Marginal | At self-cleaning threshold |
| 4:12 | 18.4° | 33.3% | Good | Standard residential, good for most racking |
| 5:12 | 22.6° | 41.7% | Excellent | Near optimal for southern U.S. latitudes |
| 6:12 | 26.6° | 50.0% | Excellent | Most common U.S. pitch, ideal production |
| 7:12 | 30.3° | 58.3% | Excellent | Near optimal for mid-latitude installations |
| 8:12 | 33.7° | 66.7% | Excellent | Excellent for northern U.S. latitudes |
| 9:12 | 36.9° | 75.0% | Good | Upper range, verify racking wind/snow loads |
| 10:12 | 39.8° | 83.3% | Good | High pitch, installer safety planning required |
| 12:12 | 45.0° | 100.0% | Marginal | Steep; structural assessment recommended |
Measure Pitch Before Ordering Racking
Most racking systems have min/max pitch ratings. A system spec'd for 2:12–12:12 cannot be used on a 1:12 roof. Always confirm pitch before placing equipment orders.
The 14.5° Self-Cleaning Rule
Panels need at least 14.5° (approx. 3:12) for rain to wash away soiling. Below this angle, plan for more frequent manual cleaning in the O&M scope.
Adjust Production for Tilt Deviation
For every 10° away from optimal tilt, expect roughly 2–5% less annual production. Use NREL PVWatts to model the exact impact for your location.
Steep Roofs Need Fall Protection
OSHA 1926.502 requires fall protection at 6:12 (26.6°) or steeper on residential roofs. Factor in anchors, harnesses, and extended labor time in your estimate.
The most common residential roof pitch in the U.S. is 6:12 (26.6°), which happens to be excellent for solar in most of the country. It falls within the 15°–40° ideal range, provides good self-cleaning, and is well within standard racking manufacturer specifications. Pitches from 4:12 to 9:12 are considered good to excellent for solar.
Yes, but flat roofs (below 2°) require ballasted racking systems that tilt the panels to 5°–20° for production and self-cleaning. The racking cost is higher and wind load analysis is required. Our calculator's "Not Recommended" rating for very low pitches refers to flush-mount systems — not tilt-frame systems on flat or low-slope roofs.
The optimal fixed tilt angle equals your latitude (approximately). For most of the continental U.S. (latitude 25°–50°), the optimal tilt is roughly 20°–40°, corresponding to roof pitches of about 4:12 to 9:12. The exact optimum is calculated using NREL's regression: 0.76 × latitude + 3.1°.
Pitches in the 40°–50° range (9:12 to 12:12) produce 3–8% less annual energy than the optimal tilt in most U.S. locations. This is because steep pitches favor winter production at the cost of summer production, slightly reducing annual totals. The impact is minor and rarely changes the economic viability of a project.
Use a digital inclinometer or pitch gauge app on your smartphone. Place your phone flat on the roof surface and read the angle in degrees. Alternatively, from the attic, measure the vertical rise over a 12-inch horizontal run using a level and tape measure. Then use this calculator to convert to all three formats.
Most standard flush-mount racking systems are rated for pitches up to 12:12 (45°). Above 12:12, you may need custom racking, structural engineering sign-off, and specialized installation procedures. Always check the specific product datasheet from your racking manufacturer.
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