Construction Calculators
Jump to a tool or explore below.
Roof Pitch Calculator
Calculate roof pitch and slope from rise and run measurements. Convert to pitch ratio, degrees, and slope percentage — plus rafter length.
Roof Pitch Calculator
Enter rise and run to calculate pitch, angle, slope, and rafter length
Vertical height
Horizontal distance
Total building width for rafter length
What Is Roof Pitch?
Roof pitch is the slope of a roof expressed as a ratio of vertical rise to horizontal run. It is one of the most important measurements in roofing because it determines material choices, drainage capability, walkability, and overall construction cost.
In the United States, roof pitch is expressed in the standard format X:12, meaning the roof rises X inches for every 12 inches of horizontal run. For example, a 6:12 pitch means the roof rises 6 inches for every 12 inches (1 foot) of horizontal distance.
Roof pitch can also be expressed as an angle in degrees or as a slope percentage. Knowing the pitch is essential for calculating rafter lengths, determining material quantities, and estimating roofing costs.
Roof Pitch Formulas
Where rise is the vertical height and run is the horizontal distance. To express as X:12, multiply the ratio by 12. To convert the angle from radians to degrees, multiply by 180/π.
Roof Pitch Chart
Complete reference table for all standard roof pitches, including angle in degrees, slope percentage, and the pitch factor (multiplier for calculating rafter length from horizontal run).
| Pitch (X:12) | Angle (°) | Slope (%) | Pitch Factor | Description |
|---|---|---|---|---|
| 0:12 | 0.00° | 0.0% | 1.000 | Flat |
| 1:12 | 4.76° | 8.3% | 1.003 | Low slope |
| 2:12 | 9.46° | 16.7% | 1.014 | Low slope |
| 3:12 | 14.04° | 25.0% | 1.031 | Low slope |
| 4:12 | 18.43° | 33.3% | 1.054 | Moderate slope |
| 5:12 | 22.62° | 41.7% | 1.083 | Moderate slope |
| 6:12 | 26.57° | 50.0% | 1.118 | Standard slope |
| 7:12 | 30.26° | 58.3% | 1.158 | Standard slope |
| 8:12 | 33.69° | 66.7% | 1.202 | Standard slope |
| 9:12 | 36.87° | 75.0% | 1.250 | Steep slope |
| 10:12 | 39.81° | 83.3% | 1.302 | Steep slope |
| 11:12 | 42.51° | 91.7% | 1.357 | Steep slope |
| 12:12 | 45.00° | 100.0% | 1.414 | Very steep |
How to Measure Roof Pitch
Method 1: From the Attic
The safest and most accurate method for measuring roof pitch:
- Go into the attic and locate an exposed rafter.
- Place a level horizontally against the underside of the rafter.
- Measure 12 inches along the level from the point where it touches the rafter.
- From the 12-inch mark, measure vertically down to the rafter — this distance is your rise.
- If you measure 6 inches of rise, your pitch is 6:12.
Method 2: From Outside
Measure from the ground or a ladder if attic access is unavailable:
- Measure the total rise (vertical height from the wall plate to the ridge).
- Measure the total run (horizontal distance from the exterior wall to the center of the roof).
- Divide the rise by the run and multiply by 12 to get the pitch in X:12 format.
Example: 8 ft rise ÷ 16 ft run = 0.5 × 12 = 6:12 pitch.
Method 3: Using a Speed Square
A speed square (rafter square) has a built-in pitch scale:
- Place the speed square's pivot point on the top edge of the rafter.
- Hold the level edge horizontal (use a level or plumb bob to verify).
- Read the pitch directly from the "Common" scale on the hypotenuse of the square.
Speed squares are available at any hardware store and provide instant pitch readings.
Common Roof Pitch Uses
Different roof pitches suit different applications, materials, and climate conditions. Here are the main categories and what they mean for your project.
L2:12 – 3:12 — Low Slope
Low-slope roofs require special materials designed to handle slow water drainage and potential ponding.
- Rubber membrane (EPDM, TPO)
- Metal standing seam
- Built-up roofing (BUR)
- Modified bitumen
S4:12 – 6:12 — Standard
The most common range for residential roofing. Compatible with nearly all roofing materials.
- Asphalt shingles
- Concrete and clay tiles
- Metal panels
- Wood shakes and shingles
H7:12 – 9:12 — Steep
Steep roofs offer excellent drainage and a premium architectural look, but cost more to install.
- Premium aesthetics and curb appeal
- Excellent water and snow shedding
- Higher installation and material cost
- Safety harnesses required for installation
V10:12+ — Very Steep
Very steep pitches are used for distinctive architectural features and specialty designs.
- Architectural features and dormers
- A-frame and chalet-style homes
- Church steeples and historic buildings
- Specialized installation techniques required
Roof Pitch Calculator FAQ
What is the most common roof pitch?
The most common roof pitches for residential homes range from 4:12 to 6:12. A 4:12 pitch (18.43°) is popular for its balance of drainage, aesthetics, and walkability. A 6:12 pitch (26.57°) is considered the standard slope and works with virtually all roofing materials.
What pitch is a 30 degree roof?
A 30-degree roof is approximately a 6.93:12 pitch — nearly 7:12. To calculate: tan(30°) = 0.577, and 0.577 × 12 = 6.93. So in practice, a 30-degree roof is built as a 7:12 pitch.
How do you calculate roof pitch from rise and run?
Divide the rise (vertical measurement) by the run (horizontal measurement), then multiply by 12 to express it in the standard X:12 format. For example, if the rise is 8 feet and the run is 16 feet: (8 ÷ 16) × 12 = 6:12 pitch.
What is the minimum roof pitch for shingles?
Most asphalt shingle manufacturers require a minimum roof pitch of 4:12 (18.43°) for standard installation. Some shingles can be installed on pitches as low as 2:12 with additional underlayment and modified installation techniques, but always check the specific manufacturer's requirements.
What is a 4/12 roof pitch in degrees?
A 4:12 (also written as 4/12) roof pitch equals 18.43 degrees. The calculation is: arctan(4 ÷ 12) = arctan(0.333) = 18.43°. This is one of the most common residential roof pitches.
How do you convert roof pitch to degrees?
Use the arctangent (inverse tangent) function: degrees = arctan(rise ÷ run) × (180 ÷ π). For a pitch expressed as X:12, the formula is: degrees = arctan(X ÷ 12) × (180 ÷ π). For example, a 6:12 pitch = arctan(6 ÷ 12) × 57.296 = 26.57°.
Need Roofing Estimation Tools?
BuildVision AI calculates roof areas, material quantities, and costs automatically from blueprints and satellite imagery.
Related Tools & Resources
Related Calculators
Software Comparisons
From the Blog
Email this calculation and keep the template
We’ll send the editable worksheet, plus pro tips to tighten your estimate.
Editable spreadsheet you can share
1:1 walkthrough with our team
Follow-up reminders so it gets done
Keep momentum on this construction calculator
We’ll send reminders, a clean export, and one pro tip to tighten your numbers.
Send this to my inbox
Share a work email and we’ll follow up with a clean copy plus next steps.