Free Rafter Calculator
Calculate rafter length, roof pitch, roof slope, rise, run, and roof angle from simple roof measurements.
Calculate Roof Rafter Measurements Easily
Our free rafter calculator helps you estimate the length of a roof rafter using the horizontal run and vertical rise. The calculator can also show roof slope, roof angle, and rise per 12 inches of run.
Enter Your Measurements
Enter the horizontal run and vertical rise of your roof.
Select Your Units
Use feet, inches, meters, or centimeters for your measurements.
Get Your Results
Calculate the estimated rafter length, slope, angle, and pitch.
Popular Roof Calculators
Use our roofing calculators to work with common roof measurements and rafter calculations.
Rafter Calculator
Calculate rafter length, roof slope, roof angle, and rise per 12 inches of run.
Use Calculator → 02Roof Pitch Calculator
Calculate roof pitch from rise and run measurements.
Use Calculator → 03Roof Slope Calculator
Calculate roof slope as a percentage from roof measurements.
Use Calculator → 04Roof Angle Calculator
Find the roof angle using horizontal run and vertical rise.
Use Calculator → 05Roof Rise Calculator
Calculate roof rise from roof pitch and horizontal run measurements.
Use Calculator → 06Roof Run Calculator
Calculate horizontal roof run from roof pitch and vertical rise measurements.
Use Calculator →How to Calculate Rafter Length
Rafter length can be estimated using the horizontal run and vertical rise of a roof.
Measure the Run
Determine the horizontal distance from the wall toward the roof ridge.
Measure the Rise
Determine the vertical height from the wall to the roof ridge.
Calculate the Rafter
Enter both measurements into our rafter calculator to get the estimated rafter length.
How Is Rafter Length Calculated?
The basic rafter length calculation uses the Pythagorean theorem. The horizontal run and vertical rise form two sides of a right triangle, while the rafter represents the hypotenuse.
For example, if the horizontal run is 12 feet and the vertical rise is 6 feet, the calculated rafter length is approximately 13.42 feet.
Calculate Your Rafter Length →Simple Tools for Common Roof Measurements
Roof Rafter Calculator is designed to make common roofing calculations easier to understand and use.
Free to Use
Calculate rafter measurements without creating an account.
Instant Results
Get calculations immediately after entering your measurements.
Multiple Units
Work with feet, inches, meters, or centimeters.
Mobile Friendly
Use the calculator on desktop, tablet, or mobile devices.
Understanding Run, Rise, Pitch, and Slope
Understanding the basic roof measurements can make rafter calculations easier.
Horizontal Run
The horizontal run is the horizontal distance used in the roof triangle calculation.
Vertical Rise
The rise represents the vertical height between the lower and higher points of the roof.
Roof Pitch
Roof pitch is commonly expressed as rise over a 12-inch horizontal run, such as 6:12.
Roof Slope
Roof slope can be expressed as a percentage based on the relationship between rise and run.
Rafter Calculator FAQ
What does a rafter calculator calculate?
A rafter calculator can estimate rafter length from horizontal run and vertical rise. It can also calculate related measurements such as roof slope, angle, and rise per 12 inches of run.
What formula is used to calculate rafter length?
The basic mathematical formula is Rafter Length = √(Run² + Rise²). This treats the run, rise, and rafter as a right triangle.
Can I use feet and inches?
Yes. The calculator supports feet, inches, meters, and centimeters and converts the measurements before performing the calculation.
Is the rafter calculator suitable for construction?
The calculator provides a mathematical estimate. Actual roof construction can involve additional factors such as overhangs, cuts, ridge boards, wall plates, building codes, and structural requirements. Verify measurements and consult a qualified professional when required.
Practical Roofing Calculation Tools
Roof Rafter Calculator provides simple online tools and educational information for common roof and rafter calculations. Our goal is to make mathematical roof calculations easier to understand and use.
Learn More About Us →Calculate Your Rafter Length
Enter your roof run and rise to get your estimated rafter length and related roof measurements.