How to Calculate Roof Pitch in Degrees

The pitch of a roof framing is its angle, usually in degrees. The roof pitch can vary from around 10 up to 45 degrees. This article will show how to calculate roof pitch in metric units and provide a helpful calculator for your convenience.

Calculating the Roof Pitch in Degrees

The formula for calculating roof pitch in degrees uses trigonometry. It requires a knowledge of the height difference between two points on a roof and the horizontal distance between them (in meters). The main calculation looks like this:

h1 – h2 = √((10/12) (a² + b²))

Where “h” is vertical distance, “√()” represents the square root operation, “a” is the horizontal dimension (in meters) and “b” is the vertical dimension (in meters).

The roof pitch in degrees can be worked out by calculating the floor of this section.

If you want to work out roof pitch by hand, measure the height difference between two points on a roof and use the same formula.

This will give you your total figure. Once you know that, divide it by the horizontal distance and then multiply it all by 57.295779513082320876798154814105 – just for fun! – and that’s how many degrees there are between those two points on your roof. Your answer should always be an exact figure. If it isn’t, your measurements are probably out of alignment.

Calculate Roof Pitch Angle with a Different Formula

To calculate roof pitch, there are different calculators available on the Internet. Once you have the measurements of both sides of your roof surface area, you can use a simple formula to calculate your values for A and B in order to find out the degrees of the pitched roofs. The formula looks like this:

A = 12 * (h1 – h2) / (10 – h2), with “A” representing the angle in degrees

B = 10 – A with “B” representing half of A

This will give you two distinct angles which, when added together equal 90° or π/2 if converting to radians. When calculating roof pitch using these formulas, ensure that your “A” value is negative if it’s for a roof that slopes downwards.

If you’re trying to calculate roof pitch expressed in degrees for a Spanish style roof, the “A” value should be positive instead.

Once you have both values, you can determine the total angle by adding them together and then converting them to degrees (or radians). For example, A = 42° and B = 32° would equal 74° as the angle of your roof (in degrees). After calculating your angles, use our calculator below to see how many meters of roofing you’ll need to complete the job.

Calculating Roof Pitch Angle with a Calculator

If you’d like to use our calculator, simply enter the height difference (in meters) and the horizontal distance between points on your roof (in meters). For example, if your roof is 9.1m high at its highest point above ground level and there are 5.7m of space between them, use 9.1 – 5.7 = 3.4m for “h” in our calculations below.

If you’re calculating roof pitch in degrees for Spanish style roofs, subtract 0.2 from your measurements before using them in the calculations below instead.

The most common angle used when planning out a roof surface area is around 20 ° (36° in degrees). The total angle of this roof is 36°, which means that you can fit two 20° slopes back to back and still be within the 90° (π/2 radians) recommended for roofs.

The width of one roll of roofing at a pitch of 20° is roughly 2.8m (3.04m at 0° roof pitch, 3.20m at 10° pitch or 3.46m at 40°), working on an average length of 15 rolls per square meter with 1mm overlap between rolls to aid weather-proofing techniques.

For calculating roof pitch in degrees for Spanish style roofs, subtract 0.06 from your measurements before using them in our calculations below instead.

pitched roof calculations in degrees
Pitched Roof Calculations

Slate Roof in Australia

One of the most popular types of roof that is used in Australia is the slates. The slates are made to be attached to the other materials that are used for the roof. These are mostly found in Australia because they can work well with the climate and environment.

Additionally, slate roofs are most often found in regions that receive heavy snowfall like Scandinavia and Northern Europe. The steep slopes prevent the weight of the entire roof from adding to the pressure on the joints which can lead to damage or leaks after there is a large amount of snow that has fallen on it.

How do You Calculate Ridge Height?

The Ridge height can be calculated by calculating the distance from the highest point on the roof pitch to the ground and subtracting the eave height.

This will give you your total figure. Once you know that, divide it by your horizontal distance and then multiply it all by 45.102670091487227814874503004864 – just for fun! – and that’s how many meters of roofing you’ll need to complete the job.

What is the Standard Roof Pitch in Australia?

The standard roof’s pitch in Australia is 30 degrees. Most roof types are built to this angle. The roof’s pitch is the amount of rising that your roof has.

What is a Roof Slope?

Roof slope is a roof’s angle. The sloped roof helps determine how much water it is capable of shedding during rainfall. In the US, the common slopes for residential roofs are 3:12, 4:12, 8:12 and 12:12 while flat roof in commercial buildings has a slope of 15:12 or 30:12. Commercial warehouses also frequently use shallower slopes like 7:12 and 10:12 to save on steel costs. There are two common methods for measuring roof slope.

Rafter Length in Australia

Rafter lengths in Australia are dependent on the type of roofing material that is attached to the rafters. When calculating the length of a rafter, it’s important to measure from the inside edges at either end. The ladder of any finish you require will need to fit between these two measurements without touching the ends of your roof.

What is Your Average Rafter Length?

On average, rafters are about 2400mm long. So count the number of lines on your rafter and use that as a guideline for calculating how many meters you need to work out how many bundles of reeds you need to buy.

The usual practice is using a bundle (0.3m) of reeds/tiles per line. So if you have a hip on a 5-line rafter, then you will need five bundles of reeds.

Flat Roof Australia

Most flat roofs in Australia occur with the use of a single layer and they are not insulated. This is because there is no requirement for insulation since you will never see this type of roof if it’s raining or snowing.

The life span of these types of roofs can vary due to how often they’re cleaned and how well they’re sealed, but it usually ranges from 10 to 30 years.

What does a Different Degree of Roof Pitch Mean?

Roof pitch is the relationship of the overall vertical distance covered by a roof to its horizontal distance span. For English style roofs, calculating roof pitch in degrees is determined by taking your height measurements at either end of the rafter (in centimetres) and calculating 75% of one measurement minus 75% of the other measurement (height divided by length).

What is a 7-degree Roof Pitch?

A 7-degree roof pitch has an angle of about 45° (π/2 radians) or 22.5° (π/4 radians) and would be considered a shallow slope. Roofs with a 7-degree pitch can be made out of any material and because of their gentle slope, they’re easier to work on than steeper pitches because you don’t have to use as many steps.

Traditional pitched roofs are often found in parts of Europe, Japan and Scandinavia where snowfall is common. In these regions, steeply sloped roofs prevent heavy accumulations from weighing down the entire roof structure which could lead to collapse or leaking after a large amount of snow has fallen on it.

What is a 15-degree Roof Pitch?

A 15-degree roof slope would have an angle of 60° (π/4 radians) which is also known as the standard domestic gable roof. Because this type of roof has such a shallow pitch, it’s easy to construct and is generally adequate for most houses.

Roofing costs on this kind of roof tend to vary quite widely because different kinds of materials will affect prices differently; however, they tend to be around the same price as those for shallower pitches due to there being less material used in calculating roofs angles A and B when calculating roofs with angles that fall between 10 and 40 degrees.

What is a 20-degree Roof Pitch?

A 20-degree roof slope would have an angle of 70° (π/3 radians) or 34.7° (2π/3 radians). Roofs with this type of gentle slope wouldn’t require any additional bracing and although they’re less common than steeper slopes, it’s usually easier to build them because you can use fewer materials in calculating the roof angle A and B when measuring roof pitch in degrees for Spanish style roofs.

Roofing costs on 20-degree roofs tend to be around the same price as those for shallower pitches if they’re made out of the same material; however, they can be more expensive if you need additional materials like plywood or metal bracing.

What is a 40-degree Roof Pitch?

A 40-degree roof pitch has an angle of 90° (π/2 radians) or 45° (π/4 radians). It’s considered an extremely steep slope that usually requires additional bracing to keep it secure or some sort of barrier at the edge for safety purposes.

Due to the additional materials required in calculating roof pitch in degrees for Spanish style roofs, roofs with a 40-degree pitch are often more expensive than other pitches.

What is a 100-degree Roof Pitch?

A 100-degree roof slope has an angle of 180° (π radians) or 90° (π/2 radians). These roofs are incredibly steep and although they look beautiful when made with traditional materials like shingles or wood, calculating roof pitch in degrees for Spanish style roofs, there’s a higher risk of poor weatherproofing leading to leaks and damage to the structure if you’re not calculating roof pitch in degrees for Spanish style roofs.

It’s best to avoid these kinds of pitches unless you’re experienced in calculating roof pitch in degrees for Spanish style roofs and can maintain it properly because slopes that fall into this category are just too steep for most people to build.

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