Free Overhang Tool

Roof Pitch Calculator with Overhang

This roof pitch calculator with overhang computes the total rafter length including the eave overhang extension beyond the exterior wall. Standard residential overhangs range from 12 to 24 inches (305–610 mm), providing weather protection and shade. The calculator determines the full rafter dimension from ridge to tail, the overhang rafter addition, soffit depth, fascia board height, and tail plumb cut angle. Proper overhang calculation ensures accurate lumber ordering and prevents rain and sun damage to exterior walls and foundations.

expand Rafter & Overhang Diagram

WALL STRUCTURAL RAFTER FASCIA SOFFIT RIDGE 18 in
Tail Length20.1 in
Fascia Drop9.0 in
Soffit Width18 in
expand Overhang Inputs
ft
: 12
in
in
straighten Rafter + Overhang Results
Structural Rafter—
Overhang Addition—
Total Rafter Length—
Fascia Drop—
Soffit Width—
Suggested Lumber—

How to Calculate Rafter Length with Overhang

Total rafter length equals the structural rafter (ridge to wall plate) plus the overhang tail (wall plate to fascia). Both sections follow the same pitch, so the overhang calculation uses the same pitch multiplier as the main roof.

tune Drag the Slider to Change Pitch
Run Rise Slope 26.57°
0.5:12 24:12
Angle 26.57°
Grade 50.0%
Multiplier 1.118
Type Conventional
1
straighten

Calculate Structural Rafter

2
expand

Calculate Overhang Addition

3
calculate

Determine Total Rafter Length

Overhang Calculation Formulas

Formulas for rafter length, soffit depth, and fascia dimensions with overhang:

straighten Overhang Rafter
Overhang Rafter = Overhang Width × Multiplier
18" × 1.118 (6:12) = 20.1" rafter addition
rotate_right Fascia Height
Fascia Drop = Overhang × (Rise ÷ 12)
18" × (6 ÷ 12) = 9" vertical fascia drop
percent Soffit Width
Soffit = Overhang Width (horizontal)
18" overhang = 18" horizontal soffit panel width
science Live Formula Calculator
ft
ft
Pitch 6 : 12
Angle 26.57°
Grade 50.0%
Rafter 13.42 ft
Multiplier 1.118

Overhang Dimensions by Pitch Chart

Click any row to see the pitch angle visualized. The chart covers all standard pitches from flat (1:12) to steep (12:12) with walkability ratings, material compatibility, and snow shedding performance.

Pitch Angle Grade Multiplier Type Walkability Snow Shedding
1:12 4.76° 8.3% 1.003 Flat/Low Easy Poor
2:12 9.46° 16.7% 1.014 Low Slope Easy Poor
3:12 14.04° 25.0% 1.031 Low Slope Easy Fair
4:12 18.43° 33.3% 1.054 Conventional Easy Fair
5:12 22.62° 41.7% 1.083 Conventional Easy Good
6:12 26.57° 50.0% 1.118 Conventional Moderate Good
7:12 30.26° 58.3% 1.158 Conventional Caution Very Good
8:12 33.69° 66.7% 1.202 Conventional Caution Very Good
9:12 36.87° 75.0% 1.250 Steep Unsafe Excellent
10:12 39.81° 83.3% 1.302 Steep Unsafe Excellent
11:12 42.51° 91.7% 1.357 Steep Unsafe Excellent
12:12 45.00° 100.0% 1.414 Steep Unsafe Excellent
6:12 — 26.57°
Compatible: All Types

FAQs

Answers to the 14 most common questions about roof pitch, slope angle, walkability, snow load, and roofing materials.

What is a standard roof overhang?

Standard residential roof overhang is 12 to 24 inches (305–610 mm). 12 inches is the minimum for weather protection. 18 inches is most common. 24 inches or more provides maximum shade and wall protection but may require additional structural support.

How do overhangs affect rafter length?

Overhangs add rafter length equal to the overhang width × pitch multiplier. An 18-inch overhang at 6:12 pitch adds 20.1 inches of rafter. At 12:12 pitch, the same overhang adds 25.5 inches. Always include overhang when ordering rafter lumber.

What is a soffit on a roof overhang?

The soffit is the horizontal underside panel that closes the gap between the fascia and the exterior wall. Soffit width equals the horizontal overhang distance. Vented soffits provide attic ventilation. The soffit is always horizontal regardless of roof pitch.

How do you cut a rafter tail for overhang?

The rafter tail cut is a plumb cut at the same angle as the main rafter plumb cut. For a 6:12 pitch, set the framing square at 6 and 12, mark the plumb line at the desired overhang distance from the bird's mouth. The tail plumb cut angle is 26.57°.

What is a bird's mouth cut?

A bird's mouth is a notch cut in the rafter where it sits on the wall top plate. It consists of a horizontal seat cut (matching the plate width) and a vertical plumb cut. The seat cut should not exceed ⅓ of the rafter depth to maintain structural integrity.

Does overhang width affect building code compliance?

Yes, overhangs wider than 24 inches may require additional engineering and may affect setback calculations. Some jurisdictions count overhangs exceeding 12–24 inches (varies by code) in the building footprint for setback measurement purposes.