Gable roof framing calculator plan diagram with full dimensions For a good straight fascia, add an extra inch or 2 to the tails of all your rafters (total length). After they're up, you can flick a line to mark and trim the tails in a nice straight line, to make up for any ridge warp or marking, cutting and fixing errors.
Use this simple tool to accurately calculate how many degrees are in any roof pitch, stair stringer, or any other slope standard or metric. Enter the values for the roof pitch in inches per foot rise. Then select a fraction if there is any.
For example: A 12/12 roof pitch would be selected as 12 inches of rise per foot with no fraction and the value generated by the calculator would be 45º. Strangely enough, if a pitch of 6 inches rise per foot is entered, then the degrees generated is not 22.5º, it is 26.6º. Furthermore, if a pitch of 3 inches rise per foot is selected, then the answer returned is 14º. It just doesn’t work that way. It takes three steps using trigonometric functions to achieve an accurate result.
For all other slopes a run must be entered. The box has a pre-defined value of 12 because rafter pitches are the primary function of this calculator. Simply click in the field inside the box and enter a value for the inches and fraction if necessary. For the complementary angle, reverse the rise and run.
The inches box will also accept decimal values making it possible to calculate the degrees for any slope!
For a quick reference for getting the angle of a pitch, use a speed square. Simply line up the common slope with any straight edge and see what degree it is on.
Roof Pitch Calculator will instantly estimate your roof slope from every possible angle.
You can calculate slope, area, rafters length and other dimensions. You can also convert roof pitch to Degrees (at the bottom).
1) Calculate Roof Slope Based On Rafters Length
Roof Span:
ft.
in.
Roof Rise:
ft.
in.
Roof Pitch = / 12″
How To Use Pitch Calculator
To estimate roof area, enter width and length (as shown in the measuring diagram below), and either Rise or Pitch – second value will auto-calculate. Click calculate. The results will pop up below the calculate button, and will include: Rafter Length, Total Size / Area, and Pitch.
Using the diagram below, measure your roof from the ground, and enter building dimensions into the calculator #2 above. Enter the span (also known as gable side width), and the rise above the base line.
To calculate your pitch and size, measure your roof and plug in your measurements in accordance with the diagram below. Enter EITHER Roof Rise or Roof Pitch.
2) Pitch to Angle (Degrees) Calculator
Enter pitch in the first box – calculation is automatic.
Enter Roof Pitch:
/ 12″
Results:
degrees angle
How To Measure Roof Rise
If you do not know the rise, and do not have a ladder or cannot access your roof in order to measure it, you can accurately estimate the rise by measuring 3 spans of siding.
Typical vinyl siding has 4″ exposure, so 3 spans would be equal to 12″ or 1 foot. Calculate the number of spans from the base line to the peak. Since most homes have a Rake wood, which is usually 6-8″ wide, you can add that width to the rise.
Example: If you have 19 spans of siding at 4″ exposure (width) of each span, and a 6″ rake board, the rise would be:
[6″ + (19 * 4″)] / 3 = 6′ 10″ roof rise.
Converting pitch (US / Canadian slope measuring method) to degrees (European slope measuring method) can be useful in figuring out the roof geometry, or for European contractors who are not accustomed to th eUS system. See Table below:
Additional Resources
To learn additional information about why roof pitch is important and different methods of calculating it, refer to our comprehensive Roof Pitch Guide.
To get roof rafters length and accurate replacement cost, use our Rafter Calculator.
If you need to to quickly estimate how much a new roof costs, use our Roof Installation Calculator
To estimate pricing for 3-tab and architectural shingles, use our Asphalt Shingles Calculator
This roofing guide is presented by Leo B. I've been a roofer for 13 years, and specialize in Metal Roofing and Flat Roofing. Have a roofing question or issue? Ask me any roofing question! Roofing Contractors - join our free Local Roofers directory to get more customers!