Rafter Length Calculator
Welcome, The Rafter Length Calculator will assists you in determining the correct length of your rafters. For the Basic Calculator, simply enter the rafter run (in feet) and the angle of the rafter (in degrees) to find the rafter length.
For a more detailed calculation, use the Advanced Calculator. Enter the total run, total rise, and pitch to get the total rafter length. Select the calculator that meets your needs, fill in the necessary fields, and obtain accurate rafter length measurements for your construction projects.
This calculator is important for building a roof, It will save your time and simplify your task. You can use this tool in two different modes basic and advance.
What Is Rafter Length
Rafter length is the distance from the roof’s edge to the ridge. It depends on the run (horizontal distance) and the angle of the rafter. Accurate calculation ensures the roof’s structural integrity.
Rafter Length Formula
Here are the formulas used in the calculator:
1. Basic Calculation Formula
Variable  Description 

Rafter Length  Length of the rafter (ft) 
Run  Horizontal distance (ft) 
Angle  Angle of the rafter (degrees) 
$\text{Rafter Length} = \frac{\text{Run}}{\cos(\text{Angle})}$
2. Advanced Calculation Formula
Variable  Description 

Total Length  Total rafter length (ft) 
Run  Horizontal distance (ft) 
Rise  Vertical distance (ft) 
Pitch  Incline of the roof (in/ft) 
$\text{Total Length} = \sqrt{\text{Run}^2 + \text{Rise}^2} + \left(\frac{\text{Pitch} \times \text{Run}}{12}\right)$
How to Use the Calculator
1. Basic Calculator:
 Enter the Rafter Run (ft) in the input field.
 Enter the Angle of the Rafter (degrees) in the input field.
 Click “Calculate” to compute the rafter length.
 View the result in the “Rafter Length” field.
2. Advanced Calculator:
 Enter the Total Run (ft) in the input field.
 Enter the Total Rise (ft) in the input field.
 Enter the Pitch (in/ft) in the input field.
 Click “Calculate” to compute the total rafter length.
 View the result in the “Total Rafter Length” field.
Calculation Examples
1. Basic Calculation Example:
Suppose you have a rafter with a run of 10 feet and an angle of 30 degrees.
Variable  Value 

Run  10 ft 
Angle  30 degrees 
 Enter
10
in the Rafter Run field.  Enter
30
in the Angle field.  Click “Calculate”.
 The rafter length is calculated as:
$\text{Rafter Length} = \frac{10}{\cos(30^\circ)} \approx 11.55 \, \text{ft}$
Calculation  Result 

$\frac{10}{\cos(30^\circ)}$

11.55 ft 
2. Advanced Calculation Example:
Suppose you have a run of 10 feet, a rise of 8 feet, and a pitch of 6 inches per foot.
Variable  Value 

Run  10 ft 
Rise  8 ft 
Pitch  6 in/ft 
 Enter
10
in the Total Run field.  Enter
8
in the Total Rise field.  Enter
6
in the Pitch field.  Click “Calculate”.
 The total rafter length is calculated as:
$\text{Total Length} = \sqrt{10^2 + 8^2} + \left(\frac{6 \times 10}{12}\right) \approx 17.33 \, \text{ft}$