PITCH SPECIFICATION & GEOMETRY

4/12 Roof Pitch: Angle, Multiplier & Shingle Standards

A 4/12 roof pitch rises 4 inches vertically for every 12 inches of horizontal run. It is one of the most common residential roof slopes in North America, representing an angle of $18.43^circ$, a slope grade of $33.33%$, and an area pitch multiplier of 1.054.

4/12 Quick Specifications

Vertical Rise: 4 inches per 12 inches of run ($1:3$ ratio)
Roof Angle: $18.43^circ$
Slope Percentage: $33.33%$ grade
Pitch Multiplier: 1.054
Walkability: Easily walkable; standard residential safety practices apply.

Material Compatibility & Code Rules for 4/12 Slopes

A 4/12 pitch is widely considered the standard threshold for residential roofing:

  • Asphalt Shingles: Permitted with standard single-layer synthetic underlayment or #15 asphalt-saturated felt (unlike 2/12–3/12 slopes which require double underlayment).
  • Metal Roofing: Fully compatible with both concealed-fastener standing seam and exposed-fastener corrugated panels.
  • Concrete & Clay Tile: Permitted under standard installation guidelines.

Area Calculation Example for a 4/12 Roof

To calculate true roof surface area for a 4/12 pitch, multiply the flat footprint area by 1.054:

$$text{Surface Area} = 2,000text{ sq ft} times 1.054 = mathbf{2,108text{ sq ft}} quad (21.1text{ Squares})$$

Calculate Your Project

Use our Roof Pitch Calculator to analyze custom dimensions, or check our Roof Pitch Chart for other slope conversions.