Measurement
What is roof pitch?
The steepness of a roof, written as a ratio the trade has used for a century — and the single number that most changes what a roof costs.
Updated September 12, 2026 · Every figure links to its source · Sources
DefinitionMeasurementAlso called: roof slope, rise over run
Roof pitch — the steepness of a roof, expressed in the United States as the number of inches the roof rises for every twelve inches of horizontal run — a 6:12 (or "6-in-12") roof rises six inches per foot; the NRCA glossary distinguishes slope (rise over run) from the older sense of pitch (rise over span), and the 2021 IRC, Section R905 uses the rise-in-twelve form to set minimum slopes for every covering.
How it is measured
Set a level horizontally against the roof surface, mark twelve inches along it, and measure straight down from that mark to the roof: the inches you measure are the pitch. A 4:12 roof is gentle, an 8:12 roof is steep enough to need roof jacks and harnesses, a 12:12 roof is 45 degrees. Converting to degrees is trigonometry — the angle whose tangent is rise divided by twelve — and the directory's roof pitch calculator does it, and the reverse, along with the multiplier that turns a roof's footprint into its true surface area.
Strictly, the trade's word for rise-over-run is "slope"; "pitch" once meant rise over the full span (so a roof rising eight feet over a 32-foot span had a one-quarter pitch). The NRCA glossary keeps both meanings. In everyday use, and in this wiki, pitch means the rise-in-twelve figure.
Why it matters
Pitch decides what may cover the roof. The IRC, Section R905 sets a minimum slope for every material: asphalt shingles need at least 2:12 (with two layers of underlayment below 4:12), clay and concrete tile at least 2½:12, wood shingles and shakes 3:12, metal panels 3:12 for lapped seams without sealant and ¼:12 for standing seam, and the membrane systems ¼:12. Below the minimum, the covering leaks whatever the workmanship; the directory's entry on minimum roof pitch for shingles covers the shingle case in detail.
Pitch also decides how the roof behaves. Steeper roofs shed water and snow faster, take hail at a glancing angle, and drain leaves; shallower roofs are easier and safer to work on, hold snow (which is a load) and give wind-driven rain more time to work under laps. In a heavy-snow region the slope is a structural question as well as a roofing one.
What it costs and who does it
Pitch enters a roofing estimate twice. First, it increases the area: a roof's surface is larger than its footprint by a factor that grows with the pitch, so the number of squares to buy and lay goes up. Second, it increases labour: above roughly 6:12 a crew must work from roof jacks and staging, moves slower and needs fall protection, and estimators apply a steep-roof rate. A very low pitch does the opposite for labour but may force a change of system. Any roofing contractor measures pitch as part of an estimate; the directory's guide to a new roof installation explains how that measurement feeds the price.
Frequently asked questions
Short answers; the sections above carry the detail and the sources.
What is a 4/12 roof pitch in degrees?
What is the minimum pitch for a shingle roof?
What is the minimum pitch for a metal roof?
Does roof pitch affect the cost of a new roof?
Next step
Find a roofer who does this
The pitch is the first thing an estimator measures. The directory lists roofing contractors by state and city.
Sources
- Roofing glossary — National Roofing Contractors Association (NRCA)
- 2021 International Residential Code, Chapter 9: Roof Assemblies — International Code Council (ICC)