

Our tool can also figure out the approximate roof truss cost. Input the roof length, the on-center spacing (the distance between the middles of two neighboring roof trusses), and the roof truss calculator will return the number of roof trusses needed. You can input the roof pitch in any of the three formats (angle, percentage, ratio), and our tool will automatically tell you the other ones.

You can input any of the three values to get the third one calculated. Here as well, our calculator works both ways. After doing that, you will see the rafter length in the bottom field. If you decided to include roof pitch in your calculations, to get the rafter length, you will need to input the run and the pitch of the roof. Please note that the rafter length calculator works both ways, that is, you can also use it to calculate the rise or the run! If you already know the rafter length and want to figure out any of the other dimensions, simply input the two you know, and you will get the third one. If you picked the rise, all you need to do is input its value, put in the roof's run, and the calculator will return the rafter length in the bottom-most field. If you want to learn more about the way it's calculated, check out our roof pitch calculator.

You can choose the rise of the roof (which is its height), or the roof pitch (which is the slope created by the rafter). Start by deciding what you want your calculations to be based on. In the field above the illustration, pick either "rafter length" or "truss count". To start your calculations, you need to choose from the two options mentioned above. You can use it either as a rafter length calculator, and get the dimensions of your trusses estimated, or as a roof truss count calculator, which will also allow you to estimate the roof truss costs and even include the price of installation.
