Roof Pitch Calculator

Calculate roof pitch, slope angle in degrees, pitch multiplier for roofing materials, and rafter length. Solve from rise/run measurements, degrees, or pitch notation (x/12).

Calculate from 3 input modes
in
How many inches of vertical rise
in
Standard run = 12 in (use 12 for x/12 notation)
ft
Half the building width (eave to ridge)
ft
Typical: 1–2 ft
Frequently asked questions
What is roof pitch and how is it measured? ›
Roof pitch is the slope of a roof expressed as a ratio of vertical rise to horizontal run. A 6/12 pitch means the roof rises 6 inches for every 12 inches of horizontal run. To measure your roof's pitch, place a level horizontally on the roof surface. Measure 12 inches along the level and then measure straight down from that 12-inch mark to the roof surface — that vertical measurement is your rise.
What pitch multiplier is used to calculate roofing materials? ›
The pitch multiplier (also called the slope factor) is the ratio of actual roof surface area to the flat footprint below it. For a 6/12 pitch, the multiplier is √(6²+12²)/12 = √(180)/12 ≈ 1.118 — meaning the actual roof surface is 11.8% larger than the footprint. Multiply your building's footprint square footage by the pitch multiplier to get the actual roof area for ordering shingles, underlayment, and other roofing materials.
What is a walkable roof pitch? ›
Roofs up to 6/12 pitch (26.6°) are generally considered walkable by experienced roofers using proper safety equipment. Pitches of 7/12 to 9/12 require fall protection and are more challenging. Anything above 9/12 (36.9°) is steep and requires special staging or equipment. For DIY roof work, 4/12 or below is manageable with care; above that, professional installation is strongly recommended for safety.
What is the minimum roof pitch for shingles? ›
Most asphalt shingle manufacturers require a minimum 2/12 pitch (with double underlayment) and recommend 4/12 or higher for best performance. At 1/12 to 2/12, the risk of water infiltration is significant and built-up roofing or a membrane system is generally preferred. Metal roofing can be installed at much lower pitches (as low as 1/4:12 for standing seam systems). Always check the specific manufacturer's requirements for your chosen roofing material.

About this roof pitch calculator

This calculator works in three modes — rise/run measurement, standard x/12 pitch notation, or degrees — and converts between all three formats. It calculates the pitch multiplier used for roofing material quantities, the rafter length including overhang, and displays a scaled roof cross-section diagram showing rise, run, and rafter.

Pitch multiplier vs. roof area

The pitch multiplier is how you convert your building's flat footprint to actual roof surface area. A 12/12 pitched roof has 41.4% more surface area than its footprint (multiplier = 1.414). A 4/12 pitch adds just 5.4% (multiplier = 1.054). This multiplier is essential for accurate material ordering — see our Roofing Calculator for a complete shingle and bundle count.