Roof framing calculator
Calculate common rafter length, pitch angle, rise, run and overhang from the roof dimensions you already know. This page uses the same shared rafter calculator as the StructCalc Android app.
Need this on site?
Get the full StructCalc Android app for offline rafter, stair, square check and jobsite layout calculators.
Free on Google Play Download StructCalcA common rafter is a right triangle: rise is the vertical height, run is the horizontal span and the rafter length is the diagonal. StructCalc accepts any two of rise, run and pitch angle, then solves the missing value before calculating the rafter length.
Add a horizontal overhang when you need the extra rafter length beyond the wall line. The calculator converts the horizontal overhang into the sloped rafter length so the number is useful for cutting and layout.
If you know the run and pitch angle, leave rise empty and StructCalc calculates the rise for you. If you know rise and run from the plans, leave pitch empty and the calculator returns the roof angle. This is useful when checking roof framing dimensions before laying out rafters.
The Android app includes common rafter and hip or valley rafter workflows, plus stairs, balusters, raked walls, square checks and measurement tools. The mobile workflow is built for quick inputs, clear results and offline use at the jobsite.
Get StructCalc on Google Play