What is Roof Pitch?

The roof pitch, also known as roof slope or roof angle, refers to the steepness or incline of a roof. It is typically expressed as a ratio, a fraction, or in degrees, indicating the vertical rise in inches for every horizontal foot. For example, a roof with a 4:12 pitch rises 4 inches vertically for every 12 inches horizontally.

The Roof Pitch Calculator is an essential tool for calculating key parameters of a roof based on its rise and run. It provides the following outputs:

1. Rafter Length: The hypotenuse or sloped length of the roof.
2. Roof Pitch (x:12): The slope expressed as a ratio (rise over a 12-inch run).
3. Roof Pitch (Degrees): The angle of the roof slope in degrees.
4. Roof Pitch (%): The slope expressed as a percentage.

Key Formulas for Roof Pitch Calculations

1. Calculate Rafter Length

The rafter length is the hypotenuse of the right triangle formed by the roof's rise and run. Using the Pythagorean theorem:

$\text{Rafter Length} = \sqrt{\text{Run}^2 + \text{Rise}^2}$

Where:

• $\text{Run}$ = Horizontal distance (in feet or inches)
• $\text{Rise}$ = Vertical height (in feet or inches)

2. Roof Pitch (x:12)

Roof pitch as x:12 expresses the slope of the roof as a ratio where the run is standardized to 12 units.

$\text{Roof Pitch (x:12)} = \frac{\text{Rise}}{\text{Run}} \times 12$

Where:

• $\text{Rise}$ = Vertical height of the roof
• $\text{Run}$ = Horizontal distance of the roof

3. Roof Pitch (Degrees)

To calculate the roof pitch in degrees, use the arctangent function:

$\text{Roof Pitch (Degrees)} = \arctan\left(\frac{\text{Rise}}{\text{Run}}\right)$

Where:

• $⁡\arctan$ = Inverse tangent function

4. Roof Pitch (%)

The slope of the roof as a percentage is calculated by dividing the rise by the run and multiplying by 100:

$\text{Roof Pitch (\%)} = \left(\frac{\text{Rise}}{\text{Run}}\right) \times 100$

Where:

• $\text{Rise}$ = Vertical height of the roof
• $\text{Run}$ = Horizontal distance of the roof

Example Calculation

Given:

• Run = 10 ft
• Rise = 6 ft

1. Rafter Length:

Using the formula:

$\text{Rafter Length} = \sqrt{10^2 + 6^2}$

$\text{Rafter Length} = \sqrt{100 + 36}$

$\text{Rafter Length} = \sqrt{136} \approx 11.66 \, \text{ft}$

2. Roof Pitch (x:12):

Using the formula:

$\text{Roof Pitch (x:12)} = \frac{6}{10} \times 12$

$\text{Roof Pitch (x:12)} = 0.6 \times 12 = 7.2$

3. Roof Pitch (Degrees):

Using the formula:

$\text{Roof Pitch (Degrees)} = \arctan\left(\frac{6}{10}\right)$

$\text{Roof Pitch (Degrees)} = \arctan(0.6) \approx 30.96^\circ$

4. Roof Pitch (%):

Using the formula:

$\text{Roof Pitch (\%)} = \left(\frac{6}{10}\right) \times 100$

$\text{Roof Pitch (\%)} = 0.6 \times 100 = 60\%$

Final Results:

For a roof with a run of 10 ft and a rise of 6 ft:

• Rafter Length: 11.66 ft
• Roof Pitch (x:12): 7.2:12
• Roof Pitch (Degrees): $30.96^\circ$
• Roof Pitch (%): $60\%$

FAQs

What is a 2/12 roof pitch?

A 2/12 roof pitch means that for every 12 horizontal units, the roof rises vertically by 2 units. This is a relatively low slope, indicating that the roof has a gentle incline.

What is the minimum pitch for a lean to roof?

The minimum pitch for a lean-to roof generally depends on the roofing material used and the climate. However, a common minimum pitch for a lean-to roof is around 1/4:12 (1/4 inch of rise per 12 inches of run) to 1:12 (1 inch of rise per 12 inches of run).

Best roof pitch for solar panels?

The absolute best roof pitch for solar panels depends on a few factors, but in general, a pitch between 30 and 40 degrees is ideal for maximizing year-round energy production