How to Calculate Roof Pitch: Complete Roofing Guide

Standing in your driveway wondering how steep your roof is?

Roof pitch matters for everything—shingle selection, cost estimates, safety requirements, and building codes.

Here's the formula:

Roof Pitch = Rise ÷ Run

Expressed as "X in 12" where X is the rise over 12 inches of horizontal run.

Let's break it down with real measurements and examples.

What Is Roof Pitch?

Roof pitch (also called roof slope) measures how steeply your roof rises.

Standard expression: "X:12" or "X/12"

Examples:

• 4:12 pitch = 4 inches of rise for every 12 inches of run
• 6:12 pitch = 6 inches of rise for every 12 inches of run
• 12:12 pitch = 12 inches of rise for every 12 inches of run (45° angle)

Key terms:

• Rise: Vertical height change
• Run: Horizontal distance
• Pitch: Rise-to-run ratio

Roof Pitch Formula

Pitch = (Rise ÷ Run) × 12

The "× 12" standardizes the run to 12 inches for easy comparison.

Alternative: You can also express as:

• Ratio: 6:12
• Fraction: 6/12 = 1/2
• Degrees: 26.57°
• Percentage: 50%

Most US builders use the X:12 format.

How to Measure Roof Pitch

Method 1: From Inside the Attic

Tools needed:

• 2-foot level
• Tape measure
• Pencil

Steps:

1. Place level horizontally against a rafter

   • Make sure bubble is centered (perfectly level)

2. Measure 12 inches from one end along the level

   • Mark this spot with pencil

3. Measure straight down from the 12-inch mark to the rafter

   • This vertical distance is your rise

4. Calculate pitch

   • If you measured 6 inches down, pitch is 6:12

Example:

• Level placed against rafter
• 12 inches horizontally along level
• 5 inches measured down to rafter
• Pitch = 5:12

Method 2: From Outside (On Roof)

Safety first: Use proper fall protection. Only for experienced roofers.

Tools needed:

• 2-foot level
• Tape measure
• Safety harness

Steps:

1. Place level on roof surface

   • Hold level perfectly horizontal (bubble centered)

2. Measure 12 inches along the level from one end

3. Measure straight down from 12-inch mark to roof surface

4. That's your rise

Example:

• 12 inches horizontal
• 4 inches down to roof
• Pitch = 4:12

Method 3: From the Ground (Pitch Gauge App)

Tools needed:

• Smartphone with pitch/angle app
• Clear view of roof edge

Steps:

1. Download a pitch finder app

   • Examples: Pitch Gauge, Roof Pitch Calculator

2. Stand back from house for clear view

3. Align phone with roof slope using app

4. App displays pitch directly

Accuracy: Good for estimates. Physical measurement more precise.

Method 4: From Roof Dimensions (Blueprint Method)

If you know:

• Total rise (peak height above wall)
• Total run (half the building width)

Formula: Pitch = (Total Rise ÷ Total Run) × 12

Example:

• Building width: 24 feet
• Run = 24 ÷ 2 = 12 feet = 144 inches
• Total rise: 72 inches (6 feet from top of wall to peak)
• Pitch = (72 ÷ 144) × 12 = 6:12

Common Roof Pitches

| Pitch | Angle (°) | Description | Common Uses | |-------|-----------|-------------|-------------| | 1:12 | 4.76° | Nearly flat | Commercial, modern homes | | 2:12 | 9.46° | Low slope | Porches, sheds | | 3:12 | 14.04° | Low | Carports, some modern homes | | 4:12 | 18.43° | Low-moderate | Ranch homes, garages | | 5:12 | 22.62° | Moderate | Standard homes | | 6:12 | 26.57° | Moderate | Very common, good drainage | | 7:12 | 30.26° | Moderate-steep | Traditional homes | | 8:12 | 33.69° | Steep | Colonial, Cape Cod styles | | 9:12 | 36.87° | Steep | Victorian, A-frame | | 10:12 | 39.81° | Very steep | Alpine, A-frame | | 12:12 | 45° | Very steep (45°) | A-frame, steep designs |

Converting Pitch to Degrees

Formula: Degrees = arctan(Rise ÷ Run)

For X:12 pitch: Degrees = arctan(X ÷ 12)

Examples:

• 4:12 pitch: arctan(4 ÷ 12) = arctan(0.333) = 18.43°
• 6:12 pitch: arctan(6 ÷ 12) = arctan(0.5) = 26.57°
• 12:12 pitch: arctan(12 ÷ 12) = arctan(1) = 45°

Quick reference:

• 1:12 ≈ 5°
• 3:12 ≈ 14°
• 6:12 ≈ 27°
• 9:12 ≈ 37°
• 12:12 = 45°

Converting Degrees to Pitch

Formula: Pitch = tan(degrees) × 12

Examples:

• 20° roof: tan(20°) × 12 = 0.364 × 12 = 4.4:12 (round to 4:12 or 4.5:12)
• 30° roof: tan(30°) × 12 = 0.577 × 12 = 6.9:12 (round to 7:12)
• 45° roof: tan(45°) × 12 = 1.0 × 12 = 12:12

Why Roof Pitch Matters

1. Shingle Selection

Low slope (2:12 to 4:12):

• Requires special underlayment
• Limited shingle options
• More leak risk without proper installation

Medium slope (4:12 to 8:12):

• Standard asphalt shingles work well
• Most common pitch range
• Good drainage and walkability

Steep slope (8:12+):

• All shingle types work
• Excellent drainage
• More materials needed due to surface area

2. Material Costs

Steeper = more materials

Formula: Multiply roof area by pitch multiplier

| Pitch | Multiplier | |-------|-----------| | 3:12 | 1.03 | | 4:12 | 1.05 | | 5:12 | 1.08 | | 6:12 | 1.12 | | 7:12 | 1.16 | | 8:12 | 1.20 | | 9:12 | 1.25 | | 10:12 | 1.30 | | 12:12 | 1.41 |

Example:

• Flat roof area: 2,000 sq ft
• Pitch: 6:12
• Actual surface area: 2,000 × 1.12 = 2,240 sq ft

You need 12% more materials due to slope.

3. Building Codes

Minimum pitch requirements:

• Asphalt shingles: 2:12 minimum (some allow 1:12 with special underlayment)
• Clay/concrete tile: 2.5:12 minimum (some 2:12)
• Metal roofing: 0.5:12 to 1:12 (depends on panel type)
• Slate: 4:12 minimum

Check local codes. Requirements vary by jurisdiction.

4. Safety and Installation Cost

Steeper = higher labor cost

Labor multipliers:

• 3:12-5:12: Standard rates
• 6:12-8:12: +10-20% labor
• 9:12-12:12: +25-40% labor
• 12:12+: +50%+ labor (safety equipment, scaffolding)

Walkability:

• Up to 6:12: Walkable with caution
• 7:12-9:12: Difficult, safety equipment needed
• 10:12+: Requires fall protection, scaffolding

5. Water Drainage

Minimum for drainage: 1:12

Lower than 1:12 risks standing water, leaks, ice dams.

Better drainage:

• 4:12+: Good drainage
• 6:12+: Excellent drainage
• 10:12+: Maximum drainage (may cause other issues)

6. Snow Load

Steeper = less snow accumulation

Snow slides off steep roofs naturally. Good for snowy climates.

But: Snow avalanche risk at entry points. May need snow guards.

Real-World Pitch Examples

Example 1: Standard Ranch House

• Measured: 5 inches rise per 12 inches run
• Pitch: 5:12
• Angle: 22.6°
• Characteristics: Walkable, good drainage, standard shingles work

Example 2: Cape Cod Style

• Measured: 8 inches rise per 12 inches run
• Pitch: 8:12
• Angle: 33.7°
• Characteristics: Steeper, safety gear needed, +15-20% material cost

Example 3: Modern Flat-Look Roof

• Measured: 1.5 inches rise per 12 inches run
• Pitch: 1.5:12
• Angle: 7.1°
• Characteristics: Low slope, special underlayment required, appears flat

Example 4: A-Frame Cabin

• Measured: 12 inches rise per 12 inches run
• Pitch: 12:12
• Angle: 45°
• Characteristics: Very steep, high material/labor cost, excellent snow shedding

Calculating Total Rise from Pitch

If you know pitch and run, find total rise:

Formula: Total Rise = (Pitch × Run) ÷ 12

Example:

• Pitch: 6:12
• Building width: 30 feet
• Run = 30 ÷ 2 = 15 feet = 180 inches
• Total Rise = (6 × 180) ÷ 12 = 1,080 ÷ 12 = 90 inches (7.5 feet)

The peak is 7.5 feet above the top of the wall.

Common Roof Pitch Mistakes

1. Measuring on old shingles

Thick layers add false height. Measure to roof deck if possible.

2. Not holding level perfectly horizontal

Tilted level gives wrong measurement. Check the bubble.

3. Measuring over uneven surface

Choose a smooth, flat section for accuracy.

4. Forgetting pitch multiplier for materials

Flat area ≠ actual roof surface. Multiply by pitch factor.

5. Using wrong angle units

Calculators default to degrees or radians. Set to degrees for roof work.

Pro Tips

Verify measurements: Take multiple readings at different roof sections. Should be consistent.

Pitch gauge tools: Speed square with pitch marks makes measurement faster.

Photography method: Take a photo from eye level across from roof. Overlay digital protractor app.

Check existing shingles: Some shingle bundles list minimum pitch on packaging.

Plan for steep roofs: Above 7:12, budget extra for safety equipment and labor.

Low-slope special care: Below 4:12, invest in quality underlayment. Leaks are more common.

Pitch and Roof Type Compatibility

Asphalt shingles: 2:12 minimum (4:12 preferred) Metal standing seam: 0.5:12 minimum Metal panels (exposed fasteners): 1:12 minimum Clay/concrete tile: 2.5:12 minimum Slate: 4:12 minimum Wood shakes: 3:12 minimum Built-up roofing (flat): 0.25:12 minimum TPO/EPDM (flat): 0.25:12 minimum

Always check manufacturer specs. Requirements vary by product.

Quick Reference

• Standard pitch formula: (Rise ÷ Run) × 12
• Common pitch: 5:12 to 7:12
• Minimum walkable: 6:12
• Steep roof: 8:12 and above
• Low slope: 3:12 and below

FAQs

Q: What's the most common roof pitch? A: 6:12 is very common for residential homes. Balances drainage, cost, and aesthetics.

Q: Can I walk on a 7:12 pitch roof? A: Yes, with caution and proper footwear. Safety harness recommended. Gets difficult above 8:12.

Q: How do I convert pitch to percentage slope? A: Divide rise by run, then multiply by 100. Example: 6:12 = (6 ÷ 12) × 100 = 50% slope.

Q: Is a steeper roof better? A: Depends. Steeper sheds snow/rain better but costs more and is harder to work on. Best pitch depends on climate, budget, and style.

Ready to calculate your roof pitch? Use our Roof Pitch Calculator for instant results, or try our Roofing Materials Calculator to estimate shingle quantities.