Rafter Length Calculator

How to Use the Rafter Length Calculator

This guide will walk you through the process of using the Rafter Length Calculator to determine various rafter measurements based on your inputs. Follow these steps carefully for accurate calculations.

Step 1: Input the Run Length

Locate the input field labeled Run Length (horizontal distance). This field requires you to enter the horizontal distance of the run. The value you enter must be a number greater than or equal to 0.1, and you can input it in increments of 0.01. This field is required, so ensure it’s filled in correctly.

Step 2: Input the Rise

Next, find the input field labeled Rise (vertical height). Enter the vertical height of the rise here. Similar to the run length, it must be a number equal to or greater than 0.1, with increments of 0.01 allowed. This is also a required field.

Step 3: Input the Overhang Length

Proceed to the input field labeled Overhang Length. This field is for entering the length of the overhang, if any. The minimum value allowed is 0, and you can specify it in increments of 0.01. Be sure to fill this out as it impacts the total length calculations.

Step 4: Select the Pitch Type

Now, choose the pitch type from the dropdown menu labeled Pitch Type. You can select from “Common Rafter”, “Hip Rafter”, or “Valley Rafter”. This choice is crucial as it will affect the subsequent calculations for hip/valley rafter lengths. This is also a required field.

Calculation Results

Once you have input all the required fields, the calculator will provide the following results:

• Pitch Angle: This is calculated using the formula atan(rise/runLength) * (180/pi) and is displayed in degrees to one decimal point.
• Pitch Ratio: Calculated as rise/runLength * 12 and presented in a “1:X pitch” format with no decimals.
• Main Rafter Length: This measures the primary rafter length using the formula sqrt(pow(runLength, 2) + pow(rise, 2)) and is shown with two decimal places.
• Total Rafter Length (with overhang): This total length includes the overhang, calculated by adding the overhang to the main rafter length.
• Hip/Valley Rafter Length: Calculated only if “Hip Rafter” or “Valley Rafter” is selected. It uses the formula sqrt(pow(runLength, 2) + pow(rise, 2) + pow(runLength, 2)).
• Total Hip/Valley Length (with overhang): Includes the overhang in the hip/valley rafter length using the formula + (overHang * sqrt(2)).

Review the results to ensure they meet your project requirements. For any doubts, repeat the steps and ensure you enter correct values in the input fields.