15 Degree Roof Pitch Calculator

Determine the rise and run measurements for a 15-degree roof pitch using this construction calculator. Roof pitch is expressed as a ratio of vertical rise to horizontal run, and a 15-degree angle corresponds to a pitch of 12:10.

What is roof pitch?

Roof pitch describes the steepness of a roof and is typically expressed as a ratio of vertical rise to horizontal run. For example, a 4:12 pitch means the roof rises 4 inches vertically for every 12 inches horizontally.

A 15-degree roof pitch is a common slope used in residential construction. It provides a balance between structural stability and cost-effectiveness, making it suitable for many building types.

Roof pitch is distinct from roof slope, which is measured in degrees. A 15-degree slope corresponds to a 12:10 pitch ratio.

How to calculate roof pitch

The relationship between roof pitch and angle can be calculated using trigonometry. For a given angle θ (in degrees), the pitch ratio (rise:run) can be determined using the tangent function:

pitch ratio = tan(θ) = rise/run

For a 15-degree roof pitch:

tan(15°) ≈ 0.2679 rise/run ≈ 0.2679 For a run of 10 units: rise ≈ 0.2679 × 10 ≈ 2.679 units

In practical terms, this means for every 10 feet of horizontal run, the roof rises approximately 2.68 feet vertically.

Step-by-step calculation

Determine the desired horizontal run distance (run)
Calculate the vertical rise using tan(15°) × run
Measure and mark the calculated rise and run on your roof structure
Ensure proper framing and sheathing are installed according to building codes

15 degree roof pitch examples

Here are some practical examples of a 15-degree roof pitch:

Run (feet)	Rise (feet)	Total Roof Length
10	2.68	10.51
12	3.22	12.50
15	4.02	15.52
20	5.36	20.64

These examples show how the vertical rise increases proportionally with the horizontal run while maintaining the 15-degree angle.

Roof pitch vs slope

While roof pitch is expressed as a ratio (rise:run), roof slope is measured in degrees. The two are related through trigonometry:

slope (degrees) = arctan(rise/run) pitch ratio = tan(slope)

A 15-degree slope corresponds to a 12:10 pitch ratio, as shown in the calculation above. Understanding this relationship helps in both design and construction planning.

FAQ

What is the pitch ratio for a 15-degree roof?: The pitch ratio for a 15-degree roof is approximately 12:10, meaning the roof rises 12 units vertically for every 10 units horizontally.
How do I convert roof pitch to degrees?: Use the formula: degrees = arctan(rise/run). For a 12:10 pitch, this gives approximately 15 degrees.
What materials are suitable for a 15-degree roof?: Common materials include asphalt shingles, metal roofing, and wood shakes. The choice depends on factors like climate, budget, and architectural style.
Is a 15-degree roof suitable for all climates?: Yes, a 15-degree roof is suitable for most climates. It provides good drainage while being cost-effective to construct.
How does roof pitch affect energy efficiency?: A steeper roof (like 15 degrees) can help with snow shedding and may slightly improve insulation, but the primary energy-saving factor is proper insulation and ventilation.