A Fundamental Explanation of Roof Pitches

Jun 4, 2021

Roof pitch is an important term in the roofing industry. It is a major factor in choosing which roofing material is right for your home. If you are in need of roof replacement, this term is something you want to be familiar with. Having a full understanding of your roofing system will help you make better buying decisions, and even influence you to stay on track with routine maintenance. Continue reading to learn more about roof pitches.


Roof pitch simply refers to the slope, angle, and slant of your roof. A roof’s pitch is represented as either two numbers divided by a slash, or as a ratio with a colon between two numbers. The first number is the numerator, and the second number is the denominator. Each number represents a specific measurement of a roof’s slope. The numerator represents the vertical height of a roof’s slant, while the dominator represents the horizontal length of a roof’s slant.

These numeric values vary a great deal depending on the construction and architecture of a home or property. There are flat roof systems with little to no slope, as well as, low-pitched roofing systems and high-pitched roofing systems. On average, most systems range in pitch from 4/12 to 8/12. Flat systems may have extremely low values, such as ¼ over 12, while other high-pitched systems may have a 12/12 value and slope down at a perfect 45 degree angle.

Doing the Math

The math can be tricky since the number 12 is the common numeric value used for slope denominators. Even though 12:12 can be reduced to 1:1, the number 12 is always used for roof pitch purposes. To read a roof pitch value, you would need to start with the top number (numerator) and finish with the bottom number (denominator).

Here are some examples:

2:12 or 2/12 = For every 12 horizontal feet, the roof drops 2 feet.

5:12 or 5/12 = For every 12 horizontal feet, it drops 5 feet.

8:12 or 8/12 = For every 12 horizontal feet, it drops 8 feet.

**Side Note: You can also say that for every 12 horizontal feet, it RISES 2 feet. It is the same either way.

Low Versus High

Low-Pitched Roofs – Homes built in the 1960’s are notorious for low-pitch roof construction. They were built with very little slope, given only enough for proper water runoff. Because these roofs have a slope around 1:12, they actually appear flat.

High-Pitched Roofs – Examples of high-pitched roofing systems would be the Victorian era of construction. Often times, these roofs were drastically angled and steep. Church steeples are another good example of a high-pitched roof.