# Roof Pitch Calculator — Convert Slope to Degrees, Percent & X-in-12

> Free roof pitch calculator: convert between x-in-12, degrees, percent grade and rise/run, read the pitch multiplier for sloped area and rafter length, and pick common pitches in one tap — all in your browser.

Convert a roof pitch between x-in-12, degrees, percent grade and rise/run — and read the slope multiplier for sloped area and rafter length.

- **HTML page:** https://siteometry.com/en/tools/roof-pitch-calculator
- **Category:** [Roofing & Siding](https://siteometry.com/en/tools/category/roofing-siding)
- **Figures live on the page:** tables, diagrams and worked figures the text refers to ("the table below") are drawn by the page and are not reproduced here. Each section below links to its anchor on the page.
- **Runs in the browser:** Siteometry calculators need no account and send no input anywhere — every number below is computed on the visitor's own device.

## How to measure roof pitch in 4 steps

1. **Hold a level horizontal** — Rest a spirit level against an exposed rafter, a gable end, or the roof surface and bring the bubble dead centre so the level is truly horizontal.
2. **Mark 12 inches of run** — Measure out exactly 12 inches along the level from the point where it touches the roof and mark it. This 12-inch run is the fixed base of the x-in-12 ratio.
3. **Measure the rise** — From the 12-inch mark, measure the vertical distance straight up (or down) to the roof line. That distance in inches is the rise.
4. **Read the pitch** — Your pitch is that rise in 12 — a 6-inch rise is 6:12. Type it into the calculator to see the angle, percentage grade, multiplier and category at once.

_On the page: https://siteometry.com/en/tools/roof-pitch-calculator#howto_

## What roof pitch is — and how to read it

Roof pitch is how steep a roof is: the vertical rise for a fixed horizontal run. Builders write it as an x-in-12 ratio — a 6:12 roof climbs 6 inches for every 12 inches of run. The same slope can be written three other ways: an angle in degrees from horizontal, a percentage grade (rise ÷ run × 100), or a reduced ratio such as 1:2. This calculator keeps all four in sync — edit any one and the others follow instantly.

One number tied to the pitch does a lot of work: the pitch multiplier. It is the factor that turns a flat, plan-view footprint into the true sloped surface, and a horizontal run into the length of rafter that spans it. A 6:12 roof has a multiplier of about 1.118, so its sloped surface is roughly 12% larger than the area it covers on the ground — which is why you order more shingles than the footprint suggests.

_On the page: https://siteometry.com/en/tools/roof-pitch-calculator#roof-pitch-intro_

## How to measure roof pitch

You do not need to climb onto the roof. The quickest method uses a level and a tape measure against an exposed rafter, a gable end, or the roof surface itself. Hold the level dead horizontal, measure out exactly 12 inches of run, then measure the vertical distance from that 12-inch mark up to the roof line. That rise, over 12, is your pitch.

_On the page: https://siteometry.com/en/tools/roof-pitch-calculator#how-to-measure_

## Common roof pitches compared

Most houses fall between 4:12 and 9:12. The scaled triangles below show how a handful of common pitches actually look, each labelled with its ratio, its angle in degrees, and its slope category — from a shallow 2:12 that barely sheds water to a dramatic 12:12 that rises at a full 45 degrees.

_On the page: https://siteometry.com/en/tools/roof-pitch-calculator#common-pitches_

## Degrees, ratio and percent reference table

The table below converts every half-step from 1:12 to 12:12 into its angle and percentage grade. Each row is generated by the same engine the calculator uses, so what you read here is exactly what the tool computes.

_On the page: https://siteometry.com/en/tools/roof-pitch-calculator#reference-table_

## Pitch categories and roofing materials

Roofers group slopes into broad categories because the pitch decides which materials will shed water reliably. Flatter roofs need fully-sealed membranes; conventional slopes suit almost everything; and every material has a minimum slope below which the manufacturer will not warrant it against leaks.

_On the page: https://siteometry.com/en/tools/roof-pitch-calculator#categories-materials_

## Frequently asked questions

### What is roof pitch?

Roof pitch is the steepness of a roof, expressed as the vertical rise over a horizontal run. Builders write it as an x-in-12 ratio — for example 6:12 means the roof rises 6 inches for every 12 inches of horizontal run. The same slope can also be given as an angle in degrees, a percentage grade, or a reduced ratio like 1:2.

### How do I measure roof pitch?

Hold a level horizontally against a rafter, gable end or the roof surface, measure 12 inches of run along it, then measure the vertical distance up to the roof at that 12-inch mark. The rise in inches over 12 is your pitch — a 6-inch rise is a 6:12 pitch. You do not need to get onto the roof; an exposed rafter in the attic works just as well.

### How do I convert roof pitch to degrees?

The angle is the arctangent of the rise divided by the run. A 6:12 pitch is about 26.6°, a 4:12 is about 18.4°, and a 12:12 is exactly 45°. Enter any x-in-12 value in the calculator and it shows the angle, percentage grade and multiplier instantly — or type the angle to convert the other way.

### What is the pitch multiplier and why does it matter?

The pitch multiplier is the factor that converts a flat footprint area into the true sloped surface area, and a horizontal run into rafter length. It equals the square root of (1 + slope²). For a 6:12 roof it is about 1.118, meaning the sloped roof surface is roughly 12% larger than the area it covers on the ground — so you multiply plan area by it to estimate roofing materials.

### What is the minimum roof pitch for asphalt shingles?

Asphalt shingles are generally suitable at 4:12 and steeper. Between 2:12 and 4:12 they can often be used with doubled underlayment (a low-slope detail), and below 2:12 they are not recommended — a membrane roof is called for instead. These are general guidelines; always follow your local building code and the shingle manufacturer's instructions.

### What counts as a flat or low-slope roof?

Roofs below about 2:12 are treated as flat and need a fully-sealed membrane or built-up system, because water drains too slowly for overlapping materials to stay watertight. Low-slope roofs, roughly 2:12 to 4:12, shed water but often need extra underlayment. From 4:12 up you are into conventional slope, where most materials work well.

### Is the calculator private?

Yes. Every calculation runs entirely in your browser. Nothing you type is uploaded to any server, and only your last-used unit choice is remembered, in your own browser's local storage.

_On the page: https://siteometry.com/en/tools/roof-pitch-calculator#faq_

## Related roofing calculators

Once you know the pitch, carry it into the calculators that turn a slope into rafter lengths, trusses, roofing quantities and drainage — these siblings pick up where the pitch leaves off.

- [Rafter Length Calculator](https://siteometry.com/en/tools/rafter-length-calculator)
- [Roofing Calculator — Pitch, Area & Materials](https://siteometry.com/en/tools/roofing)
- [Roof Truss Calculator — How Many Trusses & Cost](https://siteometry.com/en/tools/roof-truss-calculator)
- [Gutter & Downspout Calculator](https://siteometry.com/en/tools/gutter-downspout-calculator)