What pitch is "normal" for a US house?

4/12 to 8/12 covers most US single-family construction. Below 4/12 is more common on additions, porches, and ranch-style. Above 8/12 is more common on Victorian, Tudor, and historic styles.

What is the maximum pitch for asphalt shingles?

Manufacturers warranty most asphalt shingles up to 21/12 (≈ 60°). Beyond that, special steep-slope detailing (sealing each tab) is required.

What is the slope factor for?

Estimating roof area from a floor footprint. If the house footprint is 1,500 ft² and the pitch is 6/12 (slope factor 1.118), the actual roof surface is ~1,677 ft².

Source for the rise/run convention?

International Residential Code (IRC) Chapter 9 (Roof Assemblies) and the National Roofing Contractors Association (NRCA) Roofing Manual define pitch ranges by roofing system.

What pitch is "normal" for a US house?

4/12 to 8/12 covers most US single-family construction. Below 4/12 is more common on additions, porches, and ranch-style. Above 8/12 is more common on Victorian, Tudor, and historic styles.

What is the maximum pitch for asphalt shingles?

Manufacturers warranty most asphalt shingles up to 21/12 (≈ 60°). Beyond that, special steep-slope detailing (sealing each tab) is required.

What is the slope factor for?

Estimating roof area from a floor footprint. If the house footprint is 1,500 ft² and the pitch is 6/12 (slope factor 1.118), the actual roof surface is ~1,677 ft².

Source for the rise/run convention?

International Residential Code (IRC) Chapter 9 (Roof Assemblies) and the National Roofing Contractors Association (NRCA) Roofing Manual define pitch ranges by roofing system.

Roof Pitch Calculator

Convert between rise/run (X/12), degrees, and % slope — all three representations of the same roof angle.

Result

Roof pitch

6.00 / 12

26.57° · 50.0% slope · slope factor 1.1180.

Pitch (rise / 12)6.00 / 12
Angle (degrees)26.565°
Angle (radians)0.46365
Slope %50.00%
Rise per 12" run6.000 in
Slope factor (rafter length per ft of run)Multiply your horizontal projection by this to get true rafter length.1.1180
Industry categorySteep conventional (6/12 - 8/12) — most US suburban roofs.

Step-by-step

atan2(6, 12) = 26.565°.
tan(26.565°) = 0.50000 = rise/run.
Rise per 12" run = tan(θ) · 12 = 6.000 in.
Slope % = tan(θ) · 100 = 50.00%.
Slope factor (rafter / run) = 1/cos(θ) = 1.1180.

How to use this calculator

Choose the input you have (rise/run from blueprints, degrees from a smart-level app, % from a topo survey).
The other two formats appear automatically.
Multiply your horizontal floor projection (in feet) by the slope factor to size rafters and roofing material.

About this calculator

Three names for the same roof angle. **Rise/run (X/12)** is the US building-trade convention — "this roof is 6 in 12" means 6 inches of rise per 12 inches of horizontal run. **Degrees** is the geometric form (6/12 = 26.57°). **Percent slope** is the civil-engineering form (6/12 = 50%). The slope factor (1/cos θ) is what you multiply the horizontal run by to get true rafter length — a 6/12 pitch makes the rafter ~12% longer than the run. The industry category line maps the pitch to the appropriate roofing system: anything ≤ 2/12 needs a built-up or membrane roof (asphalt shingles fail at low slope); 4-8/12 is standard shingle territory; 12/12+ may need fall protection.

Frequently asked

Tradesperson convenience. A framing square has a 12" leg; setting the rise on it directly gives the cut angle for rafters. The "/12" denominator stays constant so two roofers can compare "6/12" vs "8/12" without re-doing the math.