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Roof Pitch Calculator

Convert between roof pitch, angle, slope factor, and grade from a single entry.

What do you know?

Rise and run

in

Roof pitch is usually written as rise in 12, so keep the run at 12 for the standard notation, or enter any positive run.

Results

6 : 12
Pitch ratio, rise per 12 of horizontal run
26.57°
Angle
1.118
Slope factor
50%
Grade

Everything is calculated in your browser. Nothing is uploaded.

How to calculate roof pitch online

  1. Choose an input

    Pick how you know the roof: a pitch ratio like 6 in 12, an angle in degrees, or the measured rise and run lengths.

  2. Enter the numbers

    Type your values into the fields and the results recalculate as you type, with no button to press.

  3. Read the conversions

    See the pitch as a rise in 12, the angle in degrees, the slope factor, and the grade percentage all at once.

  4. Copy the summary

    Click Copy summary to put every value on your clipboard, ready to paste into an estimate or a note.

Why use this tool

Three ways to enter a roof

Start from a pitch ratio, an angle in degrees, or measured rise and run lengths, whichever figure you already have.

Every conversion at once

A single entry returns the pitch ratio, angle, slope factor, and grade percentage together, so you never convert by hand.

Rafter length from measurements

In rise and run mode the tool also returns the sloped rafter length using the right-triangle relationship between rise, run, and slope.

Handles flat and steep alike

A flat roof reads as 0 in 12, and steep pitches stay exact right up to a vertical wall, which it flags instead of dividing by zero.

Runs entirely in your browser

Everything happens on your device; nothing is uploaded.

About this tool

Roof pitch describes how steep a roof is, usually written as the number of units it rises for every 12 units it runs horizontally, such as 6 in 12. The same slope can also be given as an angle in degrees, as a slope factor that multiplies a flat area to get the sloped area, or as a grade percentage. This calculator converts between all of those from a single entry, so a figure written one way on a plan becomes every other form instantly.

Enter whichever value you have. If you know the ratio, type the rise and the run. If you measured the roof, switch to rise and run lengths and you also get the sloped rafter length, which follows the right-triangle relationship between rise, run, and slope. If a drawing only gives the angle, the angle mode turns it back into a ratio and grade. The math is straightforward division and trigonometry, and it runs the moment you type. For a plain rise-to-run ratio without the roofing context, the ratio calculator reduces any two numbers, and the triangle calculator solves the full set of sides and angles when you know a couple of them.

Zero and negative inputs are handled cleanly. A run of zero is a vertical wall rather than a slope, and negative lengths are rejected with a short note instead of a wrong answer. Numbers large enough to overflow are flagged too, so you never see a broken result.

Frequently asked questions

What does a roof pitch like 6 in 12 mean?
It means the roof rises 6 units for every 12 units of horizontal run. The first number is the rise and 12 is the standard run used in roofing, so 6 in 12 is a moderate slope of about 26.6 degrees.
How do I convert roof pitch to an angle?
The angle is the arctangent of the rise divided by the run. Enter your pitch ratio and the calculator shows the angle in degrees automatically, along with the slope factor and grade.
What is the slope factor used for?
The slope factor is the sloped length divided by the flat run. Multiply a flat, plan-view area by the slope factor to estimate the actual sloped roof area when ordering materials.
What inputs are supported?
You can enter a pitch ratio as rise and run, an angle in degrees between 0 and 90, or measured rise and run lengths in any unit. A rise of zero is treated as a valid flat roof.
Is my data uploaded anywhere?
No. Everything runs in your browser; nothing is sent to a server.
What happens with a run of zero or negative numbers?
A run of zero is a vertical wall, so the tool says so instead of dividing by zero, and negative lengths are rejected with a short message rather than a misleading result.

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