Roof Pitch Calculator

Calculation Steps

Step 1: Measure the rise and run of the roof.

Step 2: Enter the values in the calculator.

Step 3: The calculator will compute the rafter length, pitch percent, pitch angle, and pitch as x:12.

Formula for rafter length: $$\text{Rafter Length} = \sqrt{\text{Rise}^2 + \text{Run}^2}$$

Formula for pitch percent: $$\text{Pitch Percent} = \left(\frac{\text{Rise}}{\text{Run}}\right) \times 100$$

Formula for pitch angle: $$\text{Pitch Angle} = \arctan\left(\frac{\text{Rise}}{\text{Run}}\right)$$

Formula for pitch as x:12: $$\text{Pitch as x:12} = \left(\frac{\text{Rise}}{\text{Run}}\right) \times 12$$

How to Calculate roofing rise and run

You can calculate the pitch of a roof by measuring its vertical rise and horizontal run. Here's what you'll need:

Rise: This is the vertical distance from the lower measurement point to the higher point. If using a level, place it at the lower measurement point and slide it upwards until it touches the higher point vertically. The distance between the end of the level and the lower point is the rise.

Run: This is the horizontal distance between the exterior wall of the building and the point directly below the rising measurement point. Essentially, you are measuring half of the roof's horizontal span.

Roof Pitch Area Multipliers

Common roof pitch multipliers can be used to calculate the total roof area.

Roof Pitch (in/12)	Multiplier
0/12	1
1/12	1.0035
2/12	1.0138
3/12	1.0308
4/12	1.0541
5/12	1.0833
6/12	1.118
7/12	1.1577
8/12	1.2019
9/12	1.25
10/12	1.3017
11/12	1.3566
12/12	1.4142
13/12	1.4743
14/12	1.5366
15/12	1.6008
16/12	1.6667
17/12	1.7341
18/12	1.8028
19/12	1.8727
20/12	1.9437
21/12	2.0156
22/12	2.0883
23/12	2.1619
24/12	2.2361

Types of Roof Shingles with Advantages and Disadvantages

Type of Shingle	Advantages	Disadvantages
Asphalt Shingles	Fire and water resistant Flexible enough to handle heavy snowfall Relatively inexpensive Available in various shapes and colors	Short lifespan Susceptible to temperature changes
Wood Shingles	Aesthetic value More environmentally friendly Easily cleaned with a pressure washer	Susceptible to fire Vulnerable to termite damage Do not handle extreme weather conditions well Replacing damaged shingles is difficult
Metal Shingles	Lightweight More durable than asphalt and wood shingles Sun-reflective properties	More expensive Very noisy during rain or hail Some metals are susceptible to denting
Clay or Concrete Tiles	Aesthetic value Non-flammable Fade-resistant Can last over 50 years	Relatively expensive Very heavy, requiring additional framing

Roof Pitch to Angle Chart

Standard Roof Pitch	Degrees	Percentage
0.25:12	1.193°	2.08 %
0.5:12	2.386°	4.17 %
1:12	4.76°	8.33 %
2:12	9.46°	16.67 %
3:12	14.04°	25 %
4:12	18.43°	33.33 %
5:12	22.62°	41.67 %
6:12	26.57°	50 %
7:12	30.26°	58.33 %
8:12	33.69°	66.67 %
9:12	36.87°	75 %
10:12	39.81°	83.33 %
11:12	42.51°	91.67 %
12:12	45°	100 %
13:12	47.29°	108.33 %
14:12	49.4°	116.67 %
15:12	51.34°	125 %
16:12	53.13°	133.33 %
17:12	54.78°	141.67 %
18:12	56.31°	150 %
19:12	57.72°	158.33 %
20:12	59.04°	166.67 %
21:12	60.26°	175 %
22:12	61.39°	183.33 %
23:12	62.45°	191.67 %
24:12	63.43°	200 %
25:12	64.36°	208.33 %
26:12	65.22°	216.67 %
27:12	66.04°	225 %
28:12	66.80°	233.33 %
29:12	67.52°	241.67 %
30:12	68.20°	250 %

What is the standard roof pitch?

The standard roof pitch is not fixed and is influenced by various factors. Specifically, climate, roofing material, and architectural style and aesthetics are key factors in determining roof pitch.

In areas with heavy snowfall, a steeper pitch helps snow slide off; whereas in windy regions, a shallower pitch may be more conducive to roof stability.

Additionally, different roofing materials have their own minimum pitch requirements for drainage and performance. For example, asphalt shingles typically require a minimum pitch of 4:12 or 6:12, while metal roofs can accommodate lower pitches. As for architectural styles, certain styles complement specific roof pitches, such as the low-pitch roofs of ranch houses and the high-pitch roofs of Victorian houses.

Therefore, when planning roof pitch, it is advisable to consult a professional architect or contractor to obtain advice that best suits your needs and geographical location.

What is the minimum roof pitch?

The minimum roof pitch also depends on the type of roofing material used.

Asphalt shingles generally require a pitch of at least 2:12 or 4:12 (depending on the manufacturer's recommendations) to ensure proper drainage and prevent leakage. In contrast, metal roofs can handle lower pitches, with some metal roofing panels suitable for pitches as low as 1:12, while other panels may require a minimum pitch of 3:12, depending on seam types and the use of lap sealants.

Membrane roofs are designed specifically for low-pitch applications, with a standard minimum pitch of approximately 1/4:12, but some insurance companies may require a steeper pitch (such as 1/2:12) for optimal performance. However, these are only general guidelines.

It is important to refer to the recommendations of specific roofing material manufacturers to understand the minimum safe pitch of their products. Additionally, be aware that local building codes may have specific requirements for roof pitch.

Therefore, when deciding on roof pitch, please consult a professional roofer or architect to ensure your roof meets all safety and performance standards.