Calcul Pente Toiture En Degré

Determining the slope of a roof in degrees is essential for construction, renovation, and maintenance projects. This calculator helps you convert roof pitch measurements into degrees, making it easier to specify materials and plan installations.

How to Calculate Roof Slope in Degrees

The slope of a roof is typically measured as a ratio (e.g., 4/12) where the first number represents the rise and the second number represents the run. To convert this ratio to degrees, you can use trigonometric functions.

Note: A 4/12 pitch means the roof rises 4 units vertically for every 12 units horizontally. This is equivalent to a 18.43° slope.

Steps to Calculate

Measure the rise (vertical distance) and run (horizontal distance) of your roof.
Divide the rise by the run to get the pitch ratio (e.g., 4/12).
Use the arctangent function to convert the ratio to degrees.

Common Roof Slopes

Pitch Ratio	Degrees	Description
1/12	4.76°	Very flat
2/12	9.46°	Flat
4/12	18.43°	Moderate
6/12	26.57°	Steep
8/12	33.69°	Very steep

Formula and Calculation

The formula to convert a roof pitch ratio to degrees is:

θ = arctan(rise/run) × (180/π)

Where:

θ = angle in degrees
rise = vertical rise of the roof
run = horizontal run of the roof
arctan = inverse tangent function
π ≈ 3.14159

For example, if your roof has a rise of 4 units and a run of 12 units:

θ = arctan(4/12) × (180/π) ≈ 18.43°

Worked Examples

Example 1: 4/12 Pitch

For a roof with a rise of 4 feet and a run of 12 feet:

θ = arctan(4/12) × (180/π) ≈ 18.43°

This is a common moderate slope used for residential roofs.

Example 2: 6/12 Pitch

For a roof with a rise of 6 feet and a run of 12 feet:

θ = arctan(6/12) × (180/π) ≈ 26.57°

This is a steeper slope often used for commercial buildings.

Frequently Asked Questions

What is a roof pitch?: A roof pitch is the slope of the roof, measured as the ratio of vertical rise to horizontal run. For example, a 4/12 pitch means the roof rises 4 units vertically for every 12 units horizontally.
How do I measure roof pitch?: To measure roof pitch, use a level and a measuring tape. Measure the vertical rise and horizontal run between two rafters or between the ridge and the eave.
What is the difference between pitch and slope?: Pitch refers to the ratio of rise to run (e.g., 4/12), while slope refers to the angle in degrees (e.g., 18.43°). The calculator converts pitch to slope.
What is a common roof slope for residential buildings?: A common residential roof slope is 4/12 (approximately 18.43°). This provides a balance between drainage and structural stability.
How do I convert degrees to pitch?: To convert degrees to pitch, use the tangent function: rise/run = tan(θ × (π/180)). For example, for a 18.43° slope, the pitch is approximately 4/12.