Roof Truss Calculator

You might have heard the term roof truss calculator before, but let’s start with the basics. What is a roof truss?

A roof truss is a framework for a roof composed of one or more triangles connected at joints called nodes. The triangle is used in roof trusses because it is the most simple geometric shape which will not distort when the length of the sides is fixed.  Trusses are used in roof structures in order to distribute the weight of the roof evenly on the load-bearing walls of the building. Additionally, the roof truss is also a major factor in the aesthetic nature of a building in that it determines the shape of the roofline.

Trusses can be built into any custom shape, which allows interesting features for your home at a lower cost. In order to determine the measurements a roof truss calculator can be used.

Information needed for the Roof Truss Calculator

Consideration of the use of the space underneath the roof is necessary as some types of truss allow for significant attic or storage space, such as the gambrel truss, which is commonly found in structures with lofts. Other types of trusses, for example, the scissor truss, allow for no attic space. Prior to the use of a roof truss calculator, many of which are available online or at your local roof truss manufacturer, one must know the type of truss that is going to be constructed. Each different type of truss requires different measurements for entry into the roof truss calculator.

Once a design or type of roof truss has been chosen, it is time to come up with the measurements needed to build or purchase the trusses. The first step is to measure the length and width of the building. Next, the wall height and roof pitch need to be determined. Finally, measure the gable overhang and the eave overhang. These calculations can then be entered into a roof truss calculator to obtain the data needed for the construction project.

There are roof truss calculators available to help determine the number of trusses that will be needed for the roof of a building. In order to use this type of calculator, the following measurements will be needed the length of the roof system, the width of the bottom, and the measurement of the trusses on the center in inches. Entering this information into the calculator will determine the number of trusses that will be needed to complete the roof plus the lineal feet of the trusses being used.

Where to find a Roof Truss Calculator

Many prefabricated roof truss manufacturers offer their potential customers a roof truss calculator which they can use to calculate the number of trusses they’ll need for their construction project.  There are also many online roof truss calculators available for the most popular types of trusses. One must decide what type of roof truss they are using prior to selecting a calculator since the calculators differ for each type of truss.  For instance, the measurements required for an attic truss calculator will differ from that of a scissor truss calculator.

The most popular types of trusses that can input into a roof truss calculator are as follows:

  • The Raised Heel Truss: This type of truss is popular in residential construction because it can span a large area and also a substantial quantity of insulation can be used under this type of truss.
  • Dropped Chord Truss: This type of truss is frequently used in hurricane-prone areas as this truss style prevents roof uplift due to wind.
  • Scissors Truss: These trusses are popular because they serve as the framework for cathedral ceilings. A drawback of the scissors truss is that it allows no room for insulation, which is frequently desired by energy-conscious homeowners.
  • Parallel Chord Truss: This type of truss is similar to the scissors truss in that it allows for a cathedral ceiling with the added benefit of the option to install insulation.

What a Roof Truss Calculator does

A very basic online roof truss calculator requires the span of the roof (measured in feet and inches), the pitch of the roof (as a measure in inches and sixteenths of an inch), and overlap as a measure in inches and sixteenths of an inch). For the person who is building their home for the first time, it might be a better option to order pre-made trusses.

Homebuilders need to know the roof span and whether or not there is a roof or attic mounted heating and air conditioning apparatus. The truss manufacturer needs to know whether the attic area will be used as living or storage space and the architectural details planned for the roof.  Additionally, the contractor needs to communicate the number of windows and doors as a proportion to the total wall area. The other information required by the manufacturer includes the wind exposure category, the building category, the desired pitch of the roof, and the building plans. You better be sure of the roof truss calculator you need so to make sure you get a good return on your investment.

Roof Truss Calculator


  1. building width
  2. slope in inches per foot
  3. truss heel height


  1. height in inches
  2. height in feet and inches
Building Width ft in n
Roof Pitch / 12
Heel Height in n


Height in
Height ft in

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