Roof Pitch Calculator

Roof Pitch:

Rise

m ▾

Run

m ▾

This roof pitch calculator is a convenient tool to help you determine the slope and rafter length needed for your roofing project. It provides the roof pitch angle as well as the rise-to-run ratio in the format x:12. Here, you will learn step-by-step how to calculate roof pitch accurately.

What is Roof Pitch?

Roof pitch is the angle of the roof created by the rafters. It can be described in two ways:

The angle between a rafter and the horizontal plane.
The ratio of the roof’s rise to its run, expressed as x:12.

You can also use an online gravel calculator to estimate gravel volume (cubic yards, cubic feet) and weight (tons, pounds) if needed for construction projects.

Example:

A roof pitch of 1:12 means that for every 36 feet of horizontal run, the roof rises 3 feet.

Categories of Roof Pitch

Flat roofs are never completely level; a slight slope is needed for drainage, usually between 1/2:12 and 2:12.
Low-pitch roofs (<4:12) are more difficult to maintain due to special materials required to prevent leaks.
Standard roofs fall between 4:12 and 9:12. They are easier to construct and safer to walk on.
High-pitch roofs (>9:12) may require extra fasteners and can reach pitches up to 21:12.
The most recommended pitch range is 4:12 to 9:12, considered the standard roof slope.
The minimum roof pitch is typically 1/4:12, often built using built-up or synthetic roofing materials.

This roof slope calculator delivers accurate measurements quickly, saving time and effort.

Roof Pitch Chart

The roof pitch chart illustrates the relationship between rise, span, and slope. It provides the rise-to-span ratios for common roof measurements:

Pitch	12	11	10	9	8	7	6	5	4	3	2	1
Degree	45	42.5	40	37	33.75	30.5	26.5	22.5	18.5	14	9.5	4.5

About Roof Pitch Calculator

This tool provides precise roof slope measurements, including rafter length, pitch angle, and rise-to-run ratio, ensuring results conform to construction standards.

How to Use the Roof Pitch Calculator

To determine roof pitch, open the calculator and enter the Rise and Run values. You can input measurements in your preferred units.

Step 1: Calculate Roof Pitch

After entering Rise and Run and selecting units, click “Calculate” to get:

Input:

Enter the rise value and choose units (m, ft, in, yd).
Enter the run value and choose units (m, ft, in, yd).
Click “Calculate” to obtain results.

Output:

Rafter length in meters or selected units.
Roof pitch angle in degrees.
Rise-to-run ratio as a percentage.
Pitch in the x:12 format.

Rafter Length, Angle, and Slope

Rafter Length: Length of the supporting beam; first output from the calculator.
Angle: Angle in degrees; useful for cutting rafters accurately.
Slope/Pitch: Roof incline. Example: rise 4 ft, run 16 ft → pitch 4/16 = 1/4. Essential for roof framing and planning.

Roof Pitch in Degrees

Pitch can also be expressed in degrees. Using the calculator or manually via trigonometry, convert rise/run to an angle. Roof pitch multiplier calculates the actual roof area:

Roof Pitch Multiplier = √((rise/run)² + 1)

Step-by-Step Roof Pitch Calculation

Using Pythagorean theorem and basic trigonometry, you can calculate roof pitch manually for right triangles.

Method to Find Roof Pitch

Pitch = Rise / Run
Rafter² = Rise² + Run²
Tan(angle) = Rise / Run
Angle = arctan(Rise / Run)
Grade (%) = (Rise / Run) × 100

Calculate Roof Pitch Using Rafter, Rise, and Run

If rafter and rise are known: Run² = Rafter² − Rise²
If rafter and run are known: Rise² = Rafter² − Run²

Manual measurement or a Roof Pitch Degree Calculator ensures safe, balanced, and accurate roof construction.

Example

Run = 6 m, Rise = 1.5 m.
Rafter length: Rafter² = 1.5² + 6² = 38.25 → Rafter ≈ 6.18 m
Pitch = Rise / Run = 1.5 / 6 = 0.25 = 25%
Angle = arctan(0.25) ≈ 14°
Pitch x:12 = 0.25 × 12 = 3 → 3:12
Final: 3:12 pitch, 25%, 14°

FAQs

How is roof pitch calculated?

Pitch is the vertical rise for every 12 inches of horizontal run. Example: 6-inch rise for 12-inch run → 6-in-12 pitch.

What is a 4/12 pitch?

Rises 4 inches for every 12 inches of run; considered moderate slope.

30° Roof Pitch?

≈ 7/12 pitch. Convert degrees to ratio: Pitch = tan(Angle) × 12

3/12 Roof Pitch

Rises 3 inches per 12 inches run; can be called "3 in 12".

Best Roofing Material for Low-Pitch Roofs?

Choose water-resistant shingles or materials designed for low slopes. Learn more.

5/12 Pitch Angle?

22.62°

7/12 Pitch Angle?

30.26°

Best Roof Pitch for Solar Panels?

30°–45° for optimal sunlight and efficiency.

Most Common Roof Pitch Angle?

Standard: 4/12 – 9/12. Below 4/12 is low-slope.

Best Roof Pitch for Snow?

3:12, 4:12, 5:12, 6:12. Steeper may cause snow slides.

Is 7/12 Walkable?

Above 7/12, walking requires safety equipment.

Pitch Formula

Circular Pitch: p = (π D) / N

Diametral Pitch: P = π / p, P = N / D

Gear Ratio: mG = NG / Np

Minimum Roof Pitch

Depends on material. Shingles: ≥1:6 (4 in rise/24 in run), standing seam metal: ≥1:4, roll roofing: ≥2:12.

Takeaway

This Roof Pitch Calculator quickly determines slope, rafter length, roof area, and other key dimensions, helping you calculate roofing material needs for your project.

References

From Wikipedia: Roof pitch – vertical rise over horizontal span.

From Hunker – By Michael Logan: How to Figure the Center Height of Rafters

From Carpentry-Pro-Framer: How to calculate roof pitch

By Delaurier Roofing: Importance of Roof Pitch