RapidKey Roof Pitch Calculator

Roof Rise

Flat Projection Length (Run)

Rafter Length (Slope)


Roof Pitch Degree

Roof Pitch Percentage

Roof Pitch Calculator for Degrees & Percentage

The RapidKey Roof Pitch Calculator helps you easily calculate the pitch of your roof. Learning how to calculate your roof pitch in degrees or percentage can be hard so using our pitch roof calculator helps simplify it! 

Knowing your roof pitch is important when building a roof to ensure you have enough fall (enough of a slope) to ensure correct drainage. In general, shallower roofs require more rafter or purlin support below as water drainage etc is slower so the load on the roof is less.

Understanding your roof pitch is also key when installation roofing sheets, like corrugated roofing sheets, to determine how many times you will need to overlap your corrugated sheets. Roof pitch is also a key factor that affects how wide you can install Polycarbonate Roofing sheets so it affects more than you might think!

Other common questions about calculating roof pitches, the standard roof pitch, the best roof pitch and more are answered below. To skip to a section just click the links below!

What is Roof Pitch?
How to calculate roof pitch?
What is the standard roof pitch?
What is the minimum roof pitch?
Can a roofs pitch be flat?
Does the recommended roof pitch change depending on roofing sheet?
What is the minimum polycarbonate roofing sheet pitch?
What is the minimum corrugated roofing sheet pitch?

What is Roof Pitch?

Roof pitch is best described simply as the angle of slope on your roof, the angle created by your roof rafters. The pitch of a roof, is mainly worked out as a percentage or more commonly in degrees. 

Ensuring you have the correct roof pitch on your roof is essential. In general, the steeper the pitch of the roof the better, obviously up to a certain level, but most roof pitches will be medium with, for example, a 12.5 degree roof pitch.

How to calculate roof pitch?

Whether you have a mono pitch roof or dual pitched roof, how you calculate roof pitch in degrees or percentage is essentially the same.

Calculating a roof pitch is all based around the Pythagoras theory which is a² + b² = c² the same formula used to calculate right angle triangles. When applying this to a roof the formula to calculate another dimension is:

rafter length² = rise² + run²
The RapidKey graphic below should where each of these dimensions come from. This formula does not calculate Roof Pitch itself which is a more complicated formula so best done easily using the RapidKey Roof Pitch Calculator above!

RapidKey Roof Pitch Calculator Guide Graphic

What is the standard roof pitch?

The standard roof pitch varies depending on the type of roof, location, country and other factors so there is no standard roof pitch that is universal.

One big factor affecting the standard roof pitch in a country is the countries climate with more snowy countries tending to have steeper pitches and more temperate climates tending towards shallower pitch or even flat roofs.

In the UK, roof pitches have traditionally range between 30° and 50° for house roofs, however, with more modern products in the market it is now possible to go even lower towards 12.5 degrees!

When constructing a lightweight roof for example a pergola roof, lean to roof or similar, using corrugated sheets or polycarbonate sheets you can go a lot shallower at closer to a 10 degree or even 5 degree slope for corrugated sheets.

What is the minimum roof pitch?

The minimum recommended roof pitch depends on roof sheet type and location so there isn't a one-size-fits-all roof pitch.

If you live in a location that gets snow commonly you will have to increase your roof pitch to allow for snow shedding. 

Can a roofs pitch be flat?

 Are flat roofs actually flat? No, even so called "flat" roofs in reality have to have a small pitch or slope for water drainage and proper water run off.

Does the recommended roof pitch change depending on the roofing sheet?

 Yes, the minimum and best pitch for your roof depending on the roofing sheet you are using. To find out more about the pitches for roofing sheets view our Roofing Technical and Installation Guides.

What is the minimum polycarbonate roofing sheet pitch?

 If you are building a polycarbonate roof, it depends on a lot of factors such as location, wind and structure but we suggest a 10 degree pitch as a rule of thumb.

You can go shallower than this in some cases but always bear in mind that you need proper water runoff and roof drainage.

What is the minimum corrugated roofing sheet pitch?

When building a corrugated bitumen roof you can go to a minimum of 5 degrees pitch if fully boarded, however, in most scenarios we recommend a 10 degree pitch or steeper.

To learn about overlapping corrugated roofing sheets, follow our How to Overlap Corrugated Roof Sheets Guide and How to video.

Would you like further help with your Roofing Project?

Simply jump on our Live Chat or via email shop@clearamber.com where our Teams will provide you with all the advice and support you require for your project.

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