Roof pitch angles and degrees conversion – The roof’s pitch is the vertical rise of the roof divided by its horizontal run or span. The pitch is also known as the ‘slope’ in stair construction and as the ‘tangent’ in geometry or trigonometry.
According to the National Association of Home Builders, 60% of homes in the United States have roofs with angles between 25 and 35 degrees. The remaining 40% of homes have roofs with angles that are either less than 25 degrees or more than 35 degrees.
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The pitch is usually expressed by the rise and followed by the run in the imperial measurement system (Used mainly in the USA). The rise is divided by 12. This gives the ratio of the incline for every 1 foot or 12 inches of run.
In countries that use the metric measurement system usually express the pitch in degree angle.
Pitch is very important for many reasons including walkability, materials used for roofing, and the proportions of the building as a whole.
This often becomes a main factor in various architectural styles like a steep pitch for Gothic architecture or a low pitch for Classical architecture. There are also more complex combinations of pitches forming distinctive roof shapes like a gambrel roof.
There are different ranges of pitch:
- Flat pitch – ½:12-2:12; (1/2 inch by 12 inches to 2 inches by 12 inches). Although this category is called ‘flat’ pitch it’s not completely flat. It’s slightly sloped in order to drain water
- Conventional slope pitch – 4:12-9:12 (4 inches by 12 inches to 9 inches by 12 inches)
- Steep slope pitch – more than 9:12 (9 inches by 12 inches
Low slope roofing at ranges of 1:12-4:12 needs special techniques and materials in order to avoid leaks and roof damage.
Here is an image to illustrate what the pitch is and what’s the corresponding degree is.
How to Convert Roof Pitch in Degrees
The easiest way to convert the roof pitch to degreed is using a roof pitch to degrees converter.
With the use of this converter, it will be easier for you to calculate many kinds of pitches such as a 30-degree roof pitch, 20-degree roof pitch, 25-degree roof pitch, or a 15-degree roof pitch.
Just insert the measure of your rise run or rafter and get the drawing for your roof.
However, you can also convert pitch to degrees by dividing the rise and run and get its corresponding measurement.
The roof pitch angle greatly factors the replacement cost of the roof. A steep roof usually sheds water quickly however it’s quite difficult to work on.
Roofs having a lower pitch are easier to work on but have a greater chance of creating water leaks as well as ice damming and so they require an intensive waterproofing system.
You will need then to use a waterproof coating solution on your roof to prevent those leaks.
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Now that we spoke about the pros and cons of different roof pitches let’s see how to do the actual calculation.
A roof pitch angle is written as 12/12, 6/12, 8/12, and so forth. But how do you determine the angle’s degree?
Here is how:
- Identify the rise and run. The rise will be equal to the amount of the incline within the given distance or the run that measures 12 inches. The 12-inch run is considered standard in roof pitch or angle terminologies. So use the 12-inch level as a constant “run” and 18-inch ruler as a variable “rise”. Find all the needed factors in order to determine the pitch angle’s degree.
- Locate its tangent or tan and follow the left row for you to read its corresponding degree. Divide its rise by run in order to get its tangent. So the term “12/12” means a rise of 12 and run of 12. When you divide 12 by 12 (rise/run), you will get tangent 1 that corresponds to 45 degrees.
Here is how you measure the angle with a tool:
Determine its angle by taking a 12-inch level and protractor up into standing seam roofs. Hold your protractor and lay it flat down on the edge of the sheet metal. Center its bottom level with the protractor’s pivot or end. now, center its horizontal bubble and read its corresponding measurement or degree. It will be less accurate on a slate or composite shingled roof since the angle of every shingle decreases the angle of the following one. You have to span 3 rows of shingles to be more accurate.
Another option is using a digital device to do that.
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How to Calculate a Roof’s Angle in Degrees From Pitch
As mentioned above, the tangent is a trigonometric term used to calculate the roof pitch in degrees. It is the number that comes out as a result of dividing the opposite side of the angle with its adjacent side.
Carpenters usually call this the “rise divided by run” or in simpler terms “rise/run”. For example, when the rise is 7 and the run is 12; when you divide these numbers, the result would be .583333 and this is the tangent.
Enter inv tan. 5833 followed by exe in your calculator. You will get the result of 30.255012, or if translated into fractions, 30 ¼.
Remember that the result is a decimal number so you need to change it into degrees, seconds, and minutes.
A circle is equal to 360 degrees or 360°, a minute is equal to 60 seconds or 60” and a degree is equal to 60 minutes or 60’.
In order to change 30.255012 into an understandable result or measurement, subtract the integer and multiply the decimal point by 60: (30.255012-30) x 60.
The result would be 15.3007 minutes. The next step that you need to do is to subtract 15 and then multiply .3007 x 60 in order to get 18 seconds.
Your final answer here would be 7/12 = 30°15’18”. Always take note that there are some programmable calculators with the button (°’”) which will help you in converting decimal degrees to minutes, seconds, and degrees automatically.
| Roof Pitch | Angles | Roof Pitch Multiplier |
| 1/12 | 4.76° | 1.0035 |
| 2/12 | 9.46° | 1.0138 |
| 3/12 | 14.04° | 1.0308 |
| 4/12 | 18.43° | 1.0541 |
| 5/12 | 22.62° | 1.0833 |
| 6/12 | 26.57° | 1.1180 |
| 7/12 | 30.26° | 1.1577 |
| 8/12 | 33.69° | 1.2019 |
| 9/12 | 36.37° | 1.2500 |
| 10/12 | 39.81° | 1.3017 |
| 11/12 | 42.51° | 1.3566 |
| 12/12 | 45.00° | 1.4142 |
Here’s a useful video on how to calculate pitch of a roof
The sum up
If you want to convert roof slope to degrees or roof pitch to degrees, it is necessary that you first identify the rise and then the run. By knowing this, converting can now be done in an easy and quick manner.
You just have to use your programmable calculator or device that features the roof pitch in degrees converter. Another way is using the tables shown above to check the corresponding numbers or measurements.
So, why the roof pitch is so important? When carpenters build a house or a building, they want to make sure that the measurements are correct so that roof problems like leaks will be avoided. They want to make sure that the roof materials will suit the measurement of the building.
Last update on 2023-07-04 / Affiliate links / Images from Amazon Product Advertising API
Hi, I’m Jim. I was a roofing constructor for 20 years, before deciding to start myrooff.com and gather the best content about roofing. I love woodworking and construction and it was only natural for me to start this passion project of mine. Thank you for visitng.