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How To Calculate Pitch Of Roof

Roof Pitch is a term describing how steep or flat your roof slope is.  The combination of two numbers are used to display or show the roof pitch.  Two most common methods (4/12 or 4:12) are used for marking the pitch of a roof.  On blue prints architects & engineers usually display the pitch of a roof in the format shown on the image where number (4) represents a rise and number (12) represents a length.  This means if a roof rises 4′ in the length of 12′, your Roof Pitch would be 4/12 or 18.43 degrees.

Calculating Peach of Roof

  1. Measure 12 inches from one end of the level and make a pencil mark on the level at that point.

  2. Place the end of the level against the bottom of a roof rafter and hold the level horizontally so that it’s perfectly horizontal.

  3. Measure straight up vertically from the pencil mark on the level to the bottom of the rafter. The resulting measurement is the roof’s rise. Its pitch is the rise measurement over a 12-inch run.

Low Pitched Roofs

A low pitched roof is anything that is any roof with a pitch of 3:12 or less. Many roofing shingles do not allow applications onto roofs at this pitch. More commonly, roll on membranes such that use heat to bond seams together is used as a roofing material.


  • Uses the least amount of roofing material
  • Easy to access and install


  • Cannot handle heavy loads
  • Shingles often not rated for shallow roofs
  • Medium-slope – 4:12 to 9:12, which are often mathematically reduced and expressed as 1:3 and 3:4. Roofs with pitches of 6:12 are the most common. A nice balance between water and snow run-off and ease of access.
  • Steep-slope – Any pitch above 9:12. These roofs may require extra fasteners, and these steeper roofs are very challenging to walk on.

How much pitch should a gutter have?

Once you’ve re-pitched your roof, the next thing to concern yourself with is the gutters. Efficient gutters have a pitch that allows rainwater to drain away from the roof and home. This is essential for preventing floods and leaks, avoiding the harm of nearby landscapes, and protecting your home’s foundation. Don’t take gutters lightly.

Most roofers will set the slope at 1 quarter inch per 10 feet of guttering. So, if you have 30 feet of guttering, your downspout should be 0.75 inches lower than the other end (0.25 x 3 = 0.75). Simple enough, right?

Roof pitches matter

Not many homeowners think about their roof pitch often (heck, not many people even know it exists), but understanding and maximizing your roof’s pitch increases your home’s longevity and lowers the amount of time you’ll have to see a roofer. Reread this article and take the time to learn more about roof pitches.

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