Roof Rafter Calculator

If you plan to use a gable roof, our roof rafter calculator tools are handy for calculating the number of rafters needed, rafter length calculator, lineal feet of rafter, board feed in ridge and sub-facia,and the total board feet in the roof.

Rise and Run means that a 6/12 pitch roof has 6" of rise (vertical) for each foot of run (horizontal).

 

ROOF RAFTER CALCULATOR
A) Roof Length In Feet	B) Rafter Length In Feet	C) On Center (inches between rafters)	D) Rafter Thickness In Inches	E) Rafter Width In Inches
ft	ft	in	in	in

Typical rafter on center spacing is 16" or 24".

How to Enter Sizes

24 Feet	24
24 Feet 6 inches	24 6
24 Feet 6 & 1/2 inches	24 6 1/2

Trying to find what size lumber to use?
This is based upon the span of the rafter (horizontal span, not total rafter length), live and dead loads. To size joists and rafters use the Maximum Span Tables for southern yellow pine. This Rafter Span Calculator is species specific for Douglas Fir, hemlock, etc.