.calc-section { margin-bottom: 25px; padding: 20px; background: #f9f9f9; border-radius: 8px; }
.calc-group { margin-bottom: 15px; }
.calc-group label { display: block; font-weight: bold; margin-bottom: 5px; color: #2c3e50; }
.calc-group input { width: 100%; padding: 10px; border: 1px solid #ccc; border-radius: 5px; font-size: 16px; box-sizing: border-box; }
.calc-btn { background-color: #0073aa; color: white; padding: 12px 24px; border: none; border-radius: 5px; cursor: pointer; font-size: 18px; width: 100%; transition: background 0.3s; font-weight: bold; }
.calc-btn:hover { background-color: #005177; }
.calc-result { margin-top: 25px; padding: 20px; border-left: 5px solid #0073aa; background: #eef7fc; }
.result-val { font-size: 24px; font-weight: bold; color: #0073aa; }
.roof-info h2 { color: #23282d; border-bottom: 2px solid #0073aa; padding-bottom: 10px; margin-top: 40px; }
.roof-info h3 { color: #23282d; margin-top: 25px; }
.roof-info table { width: 100%; border-collapse: collapse; margin: 20px 0; }
.roof-info th, .roof-info td { border: 1px solid #ddd; padding: 12px; text-align: left; }
.roof-info th { background-color: #f2f2f2; }
.roof-info ul { padding-left: 20px; }
.roof-info li { margin-bottom: 10px; }
function calculateRoofPitch() {
var rise = parseFloat(document.getElementById('riseInput').value);
var run = parseFloat(document.getElementById('runInput').value);
var resultDiv = document.getElementById('resultDisplay');
if (isNaN(rise) || isNaN(run) || run <= 0) {
alert("Please enter valid positive numbers for Rise and Run.");
return;
}
// Standard pitch calculation (normalized to x:12)
var normalizedRise = (rise / run) * 12;
var angleRad = Math.atan(rise / run);
var angleDeg = angleRad * (180 / Math.PI);
var percent = (rise / run) * 100;
document.getElementById('pitchRatio').innerHTML = normalizedRise.toFixed(2) + " : 12";
document.getElementById('pitchAngle').innerHTML = angleDeg.toFixed(2);
document.getElementById('pitchPercent').innerHTML = percent.toFixed(2);
var category = "";
if (angleDeg = 9.5 && angleDeg <= 37) {
category = "Conventional Slope (Common for asphalt shingles)";
} else {
category = "Steep Slope (Often seen on Victorian or Tudor styles)";
}
document.getElementById('pitchCategory').innerHTML = category;
resultDiv.style.display = 'block';
}
Roof Pitch Calculator
Standard run is usually 12 inches for the pitch ratio (x:12).
Roof Pitch Ratio:
Angle in Degrees: °
Slope Percentage: %
Category:
How to Calculate Roof Pitch
Roof pitch is a numerical representation of the steepness of a roof. It is expressed as a ratio of the "rise" (vertical height) over the "run" (horizontal distance). In the United States, the standard unit of measurement is inches, and the run is almost always expressed as 12 inches.
The Pitch Formula
To find your roof pitch ratio manually, use this formula:
Pitch = Rise / (Run / 12)
3 Simple Steps to Measure Roof Pitch
- Access the Attic: Measure from the base of a rafter (where it meets the wall) horizontally for 12 inches. This is your Run.
- Measure Up: From that 12-inch horizontal mark, measure straight up to the bottom of the rafter. This vertical measurement is your Rise.
- Determine the Ratio: If your rise is 6 inches and your run is 12 inches, your pitch is 6/12 (or 6:12).
Common Roof Pitch Classifications
| Pitch Ratio | Angle (Degrees) | Classification |
|---|---|---|
| Flat (0/12 to 2/12) | 0° – 9.5° | Often requires EPDM or TPO roofing. |
| Low Slope (2/12 to 4/12) | 9.5° – 18.4° | Requires specific shingle underlayment. |
| Medium Slope (4/12 to 9/12) | 18.4° – 36.9° | Standard for most residential homes. |
| Steep Slope (9/12+) | 36.9°+ | Difficult to walk on; requires safety harnesses. |
Why Pitch Matters
Calculating your roof pitch correctly is vital for several reasons:
- Material Selection: Not all materials work on all slopes. For instance, standard asphalt shingles are generally not recommended for pitches below 2/12 because they can leak.
- Water Drainage: Steeper roofs shed water and snow much faster than flatter roofs, reducing the risk of ice damming.
- Cost Estimation: Contractors often charge more for "steep charges" because working on high-pitch roofs is more dangerous and requires more safety equipment.
- Surface Area: The steeper the pitch, the more roofing material (squares) you will need to cover the same horizontal footprint.
Example Calculation
If you have a roof that rises 8 inches for every 12 inches of horizontal run:
- Divide 8 by 12 = 0.666.
- Use the Arctan function (tan⁻¹) of 0.666 to find the angle.
- The result is approximately 33.69 degrees.
- This is considered a "8/12" pitch, which is a standard medium-to-steep residential slope.