How to Calculate the Dimensions of a Roof Pitch in Degrees?

Roof Angles in Degrees This roof pitch calculator is a handy tool that will help you quickly assess the pitch of your roof and what length rafters you need for your construction works. We will explain to you how to determine the roof pitch step by step. You can also use this roof slope calculator to recalculate the roof pitch from degrees to percents.

To estimate the total cost of the roof, you may want to switch to the roofing calculator instead. We also have a dedicated roof truss calculator that is an excellent tool for finding roof truss expenses.

What Is the Roof Pitch?

A 4/12 is a roof slope that rises by 4 inches for every 12 inches across. This forms an angle of 18.5° between the horizontal section and the roof, and creates a gentle incline that is seen as a midpoint between a low-pitch and medium-pitch roof. A 4/12 slope is enough to accommodate water runoff, but is not suitable for regions that are affected by heavy snowfall. Standard asphalt and composition shingles are the best for a 4/12 roof; rubber and wood shingles are unsuitable.

Roof pitch is simply the slope created by the rafter. It can be assessed in two ways – either as the angle the rafter makes with the horizontal or the proportion between the rise and the run of the roof.

Roof pitch is often expressed as a ratio between rise and run in the form of x:12. For example, a pitch of 1:12 means that for every twelve yards of building length, the rise will be equal to one yard.

We can divide roofs into the following categories:

Flat roofs are not perfectly flat in reality – they need a small slope for water runoff. Generally, these roofs have a pitch from 1/2:12 to 2:12 (from 4.2% to 16.7%).
Low pitched roofs have the pitch below 4:12 (33.3%). These are generally difficult to maintain, as they require special materials to avoid leaks.
Conventional roofs have the pitch ranging from 4:12 to 9:12 (33.3% to 75%). They are the easiest ones to construct, and they are safe to walk on.
High-pitched roofs often require additional fasteners. They have a pitch that can be as high as 21:12 (175%).

Also Read: How to Stop Stairs Creaking

How to Calculate Roof Pitch?

Generally, roof pitch is calculated from the same formula that describes a right triangle (you can find more information about it in the right triangle calculator). You can use the following equations to find the length of the rafter and the slope:

Roof Slope Calculator – Example of Use

1. Measure the run length – it is the horizontal distance between the roof ridge and the wall of the building. Let's assume it is equal to 6 m. Measure the rise of your roof. Let's say it is equal to 1.5 m.
2. Calculate the rafter length, substituting these values into the following formula:
3. rafter² = rise² + run² = 1.5² + 6² = 2.25 + 36 = 38.25
4. rafter = √38.25 = 6.18 m
5. Calculate the roof pitch as the proportion of rise and run: pitch = rise / run = 1.5 / 6 = 25%
6. Recalculate this value into an angle:
7. angle = arctan(pitch) = arctan(0.25) = 14°
8. Finally, you can find the roof pitch in the form of x:12. x = pitch * 12 = 0.25 * 12 = 3
9. The pitch of your roof is 3:12. It can also be written down as 25% or 14°.

What Is the Standard Pitch for a Roof?

There is no standard, universal roof pitch. Roof pitch varies depending on culture, climate, style, and available materials. In the USA, the range of standard pitches is anywhere between 4/12 and 9/12. In the UK, the typical house has a pitch between 40°-50° – although 45° should be avoided.

Contemporary houses often have ‘flat roofs’ which shouldn't be completely flat but should be around 1:40. In Italy, with its more temperate climate, the range of angles is 16-25.

Also Read: Corner Windows Cost

What Is the Average Quote for Getting a Roof Pitched?

There are a lot of factors that will affect how much getting your roof pitched will cost – design, style, accessibility, cost of labor etc. In the USA, you can expect to pay between $3.19-$4.43 per sq.ft. for asphalt shingles. If you choose another material, such as metal or wood, the range is $7.35-$10.73 per sq.ft.

In the UK, the price of getting a roof fitting is £72-£75 per square meter. These are only estimates though, talk to your neighbors to see what roofing costs in your area.

What Is the Minimum Roof Pitch for Snow?

The minimum roof pitch for shedding snow is around 30°, or a 6:12 or 7:12 slope. However, this is not a definite, as the material of your roof, the direction of the snow and wind are some factors that can affect whether or not snow will slide, as roofs of as little as 10° have been reported to shed snow. Roofs of steeper pitches will likely retain less snow, so, if you live in snow-prone regions, a steeper pitch is highly desired.

Also Read: Pea Gravel Weight Per Yard