---
title: "Roof pitch chart: degrees, slope and rafter multiplier"
description: "A roof pitch chart from 1/12 to 24/12: the angle in degrees, slope percent, plumb and seat cuts, and rafter length per foot of run. Free printable PDF."
canonical: https://klmlabs.app/construction-calculator/roof-pitch-chart/
updated: 2026-11-07
---

# Roof pitch chart: degrees, slope and rafter length

Pitch is the rise in inches per foot of run: a 6/12 roof climbs 6" per foot. The chart gives the angle, slope and rafter length from 1/12 to 24/12.

Download the printable chart (PDF, US Letter, 1 page, 32 KB): https://klmlabs.app/construction-calculator/charts/roof-pitch-chart.pdf. Every number is worked out by Construction Calculator 1.1.1's own formulas.

## Roof pitch to degrees, slope and rafter length, 1/12 to 24/12

| Pitch | Angle (plumb cut) | Seat cut | Slope | Rafter per foot of run | Multiplier |
|---|---:|---:|---:|---:|---:|
| 1/12 | 4.8° | 85.2° | 8.3% | ≈ 12-1/16" | 1.0035 |
| 2/12 | 9.5° | 80.5° | 16.7% | ≈ 12-3/16" | 1.0138 |
| 3/12 | 14° | 76° | 25% | ≈ 12-3/8" | 1.0308 |
| 4/12 | 18.4° | 71.6° | 33.3% | ≈ 12-5/8" | 1.0541 |
| 5/12 | 22.6° | 67.4° | 41.7% | 13" | 1.0833 |
| 6/12 | 26.6° | 63.4° | 50% | ≈ 13-7/16" | 1.118 |
| 7/12 | 30.3° | 59.7° | 58.3% | ≈ 13-7/8" | 1.1577 |
| 8/12 | 33.7° | 56.3° | 66.7% | ≈ 14-7/16" | 1.2019 |
| 9/12 | 36.9° | 53.1° | 75% | 15" | 1.25 |
| 10/12 | 39.8° | 50.2° | 83.3% | ≈ 15-5/8" | 1.3017 |
| 11/12 | 42.5° | 47.5° | 91.7% | ≈ 16-1/4" | 1.3566 |
| 12/12 | 45° | 45° | 100% | ≈ 17" | 1.4142 |
| 13/12 | 47.3° | 42.7° | 108.3% | ≈ 17-11/16" | 1.4743 |
| 14/12 | 49.4° | 40.6° | 116.7% | ≈ 18-7/16" | 1.5366 |
| 15/12 | 51.3° | 38.7° | 125% | ≈ 19-3/16" | 1.6008 |
| 16/12 | 53.1° | 36.9° | 133.3% | 20" | 1.6667 |
| 17/12 | 54.8° | 35.2° | 141.7% | ≈ 20-13/16" | 1.7341 |
| 18/12 | 56.3° | 33.7° | 150% | ≈ 21-5/8" | 1.8028 |
| 19/12 | 57.7° | 32.3° | 158.3% | ≈ 22-1/2" | 1.8727 |
| 20/12 | 59° | 31° | 166.7% | ≈ 23-5/16" | 1.9437 |
| 21/12 | 60.3° | 29.7° | 175% | ≈ 24-3/16" | 2.0156 |
| 22/12 | 61.4° | 28.6° | 183.3% | ≈ 25-1/16" | 2.0883 |
| 23/12 | 62.4° | 27.6° | 191.7% | ≈ 25-15/16" | 2.1619 |
| 24/12 | 63.4° | 26.6° | 200% | ≈ 26-13/16" | 2.2361 |

Rafter lengths to the nearest 1/16" (≈ when rounded), with no overhang. The multiplier is feet of rafter per foot of run.

## Common rafter length by span and pitch

| Building span | 4/12 | 6/12 | 8/12 | 10/12 | 12/12 |
|---|---:|---:|---:|---:|---:|
| 12 ft | ≈ 6' 3-7/8" | ≈ 6' 8-1/2" | ≈ 7' 2-9/16" | ≈ 7' 9-3/4" | ≈ 8' 5-13/16" |
| 16 ft | ≈ 8' 5-3/16" | ≈ 8' 11-5/16" | ≈ 9' 7-3/8" | ≈ 10' 4-15/16" | ≈ 11' 3-3/4" |
| 20 ft | ≈ 10' 6-1/2" | ≈ 11' 2-3/16" | ≈ 12' 0-1/4" | ≈ 13' 0-3/16" | ≈ 14' 1-11/16" |
| 24 ft | ≈ 12' 7-13/16" | ≈ 13' 5" | ≈ 14' 5-1/16" | ≈ 15' 7-7/16" | ≈ 16' 11-5/8" |
| 28 ft | ≈ 14' 9-1/16" | ≈ 15' 7-13/16" | ≈ 16' 9-15/16" | ≈ 18' 2-11/16" | ≈ 19' 9-9/16" |
| 32 ft | ≈ 16' 10-3/8" | ≈ 17' 10-11/16" | ≈ 19' 2-3/4" | ≈ 20' 9-15/16" | ≈ 22' 7-1/2" |

The run is half the span. Lengths go from the outside of the wall to the center of the ridge, to the nearest 1/16", with no overhang.

## What is a 4/12 roof pitch?

It rises 4" per foot of run: an angle of 18.4° and a 33.3% slope. Each foot of run takes about 12-5/8" of rafter, a multiplier of 1.0541.

## What is a 6/12 roof pitch?

It rises 6" per foot of run: an angle of 26.6° and a 50% slope. Each foot of run takes about 13-7/16" of rafter, a multiplier of 1.118.

## What's a normal pitch for a roof?

There isn't one. The code sets only the lowest pitch for each roofing:

| Roofing | Lowest pitch |
|---|---|
| Mineral-surfaced roll roofing | 1/12 |
| Asphalt shingles | 2/12, with double underlayment up to 4/12 |
| Clay and concrete tile | 2-1/2/12, with double underlayment up to 4/12 |
| Metal roof shingles | 3/12 |
| Wood shingles and shakes | 3/12 |
| Slate | 4/12 |

From the 2021 IRC, R905. Check your local code and the roofing maker's instructions.

## How do I turn pitch into degrees?

Find your pitch in the chart: 8/12 is 33.7° and a 66.7% slope. Its multiplier is 1.2019, about 14-7/16" of rafter per foot of run.

## How do I work out rafter length?

Multiply the run (half the span) by the multiplier. A 24' span at 6/12 is a 12' run: 12 × 1.118 is 13.42 ft, about 13' 5". That is the length to the center of the ridge.

Then take off half the ridge board's thickness, measured level. For a 1-1/2" ridge, that is 3/4" off the run, about 13/16" along a 6/12 rafter.

Rafter size comes from your code's span tables, not the pitch.

## What angle are the plumb and seat cuts?

The plumb cut at the ridge is the roof's angle. The seat cut on the wall is 90° minus that. At 6/12 they are 26.6° and 63.4°; at 12/12 both are 45°.

## Work out your own with Construction Calculator

- Pitch from rise and run, or rise from pitch
- Hip, valley and jack rafters, with their cuts
- Send a length to the calculator to add an overhang

Download Construction Calculator on the App Store: https://apps.apple.com/us/app/fraction-feet-inch-calculator/id6816445977

Free to download, with in-app purchases. Every feature, the calculator included, needs the free trial or a purchase: Yearly US$9.99 a year with a 7-day free trial for eligible new subscribers, or Lifetime US$19.99 paid once (US prices). iPhone and iPad, iOS 17.0 or later. All the facts: https://klmlabs.app/construction-calculator/

## The facts this page states, with sources

As KLM Labs' fact record words them; the page may put them in its own words. Construction Calculator's facts page: https://klmlabs.app/construction-calculator/

- 11 tools, from stairs, roof pitch and rafters to concrete, board feet and miters. (Source: [Apple's app lookup](https://itunes.apple.com/lookup?id=6816445977&country=us).)
- Hold a tool's length, area or volume to send it to the calculator. (Source: [Apple's app lookup](https://itunes.apple.com/lookup?id=6816445977&country=us).)
- Every tool opens a short guide with a worked example. (Source: [Apple's app lookup](https://itunes.apple.com/lookup?id=6816445977&country=us).)
- IRC 2021 R905 minimum slopes: asphalt shingles 2/12 (double underlayment from 2/12 up to 4/12), clay and concrete tile 2-1/2/12, metal roof shingles 3/12, mineral-surfaced roll roofing 1/12, slate 4/12, wood shingles and wood shakes 3/12. (Source: https://up.codes/viewer/colorado/irc-2021/chapter/9/roof-assemblies (the 2021 IRC as adopted without amendments; read 2026-11-06).)
- IRC 2024 keeps the R905 minimum slopes (R905.2.2 to R905.8.2) and R802.4.1 rafter sizing with the same numbers and values. (Source: https://up.codes/viewer/texas/irc-2024/chapter/9/roof-assemblies and https://up.codes/viewer/texas/irc-2024/chapter/8/roof-ceiling-construction (the 2024 IRC adopted without amendments; read 2026-11-07).)
- IRC 2021 R802.4.1: rafters are sized from the rafter span tables R802.4.1(1) to (8), or the AWC Span Tables for other grades, species and loads. (Source: https://up.codes/viewer/colorado/irc-2021/chapter/8/roof-ceiling-construction (read 2026-11-06).)
- A common rafter's line length runs to the ridge's center; it is shortened by half the ridge thickness, measured level (at right angles to the plumb cut). (Source: Griffith, Carpentry §19 (https://chestofbooks.com/home-improvement/woodworking/Ira-S-Griffith/Carpentry/19-Ridge-Piece.html); Sloggatt, Common Rafter Framing (https://www.thisiscarpentry.com/2012/11/09/common-rafter-framing/); both read 2026-11-07.)

## More construction charts

- [Stair rise and run code: 7-3/4" risers, 10" treads](https://klmlabs.app/construction-calculator/stair-rise-and-run/): The 2021 IRC limits for stair risers (7-3/4" max) and treads (10" min), the 7-11 rule, and worked stair layouts for rises from 2' to 10'. Free PDF.
- [Crown molding angles chart: miter and bevel settings](https://klmlabs.app/construction-calculator/crown-molding-angles/): Miter and bevel settings for 52/38 and 45/45 crown molding cut flat on a compound miter saw, for wall corners from 60° to 150°. Free printable chart.
- [Fraction to decimal chart: inches, millimeters and feet](https://klmlabs.app/construction-calculator/fraction-decimal-inch-chart/): A fraction to decimal chart for every 64th of an inch, with millimeters and decimal feet, plus inches to decimal feet. Free printable PDF, US Letter.
- [How to calculate board feet](https://klmlabs.app/construction-calculator/board-feet/): A board foot is 144 cubic inches of lumber, 12" × 12" × 1". How to calculate board feet from nominal sizes, with a printable chart for 1x4 to 6x6.
- [How many bags of concrete in a yard?](https://klmlabs.app/construction-calculator/concrete-bags-per-yard/): About 45 bags of 80 lb concrete make a cubic yard, 60 of 60 lb, 90 of 40 lb. A slab chart in yards and bags with 10% waste, as a free printable PDF.
- [How to calculate square footage from inches and fractions](https://klmlabs.app/construction-calculator/square-feet-from-feet-and-inches/): Multiply length × width in inches and divide by 144 for square feet. Worked examples with feet, inches and fractions, done exactly, and a printable chart.

All 7 construction charts: https://klmlabs.app/construction-calculator/guides/

## Sources

1. [International Code Council: 2021 IRC, Chapter 9, Roof Assemblies (R905 minimum slopes; the official text)](https://codes.iccsafe.org/content/IRC2021P2/chapter-9-roof-assemblies)
2. [UpCodes: 2021 IRC Chapter 9 as adopted without amendments (R905.2.2, R905.3.2, R905.4.2, R905.5.2, R905.6.2, R905.7.2, R905.8.2, read in full)](https://up.codes/viewer/colorado/irc-2021/chapter/9/roof-assemblies)
3. [UpCodes: 2021 IRC Chapter 8, Roof-Ceiling Construction (R802.4.1 rafter size)](https://up.codes/viewer/colorado/irc-2021/chapter/8/roof-ceiling-construction)
4. [Ira S. Griffith, Carpentry, §19 Ridge Piece: a common rafter is shortened by "one-half the thickness of the ridge measured at right angles to the plumb cut"](https://chestofbooks.com/home-improvement/woodworking/Ira-S-Griffith/Carpentry/19-Ridge-Piece.html)
5. [Mike Sloggatt, Common Rafter Framing, THISisCarpentry (the ridge's full width comes off the building width before it is halved into each rafter's run)](https://www.thisiscarpentry.com/2012/11/09/common-rafter-framing/)
6. [UpCodes: 2024 IRC Chapter 9 as adopted without amendments (Texas Windstorm Insurance Association; R905 minimum slopes)](https://up.codes/viewer/texas/irc-2024/chapter/9/roof-assemblies)
7. [American Wood Council: Span Tables for Joists and Rafters, 2024 edition](https://awc.org/resources/2024-span-tables/)
8. [Fraction Feet Inch Calculator (Construction Calculator) on the App Store](https://apps.apple.com/us/app/fraction-feet-inch-calculator/id6816445977)

Last updated November 7, 2026.