To determine roof rafter length, you need to know the following four measurements:ġ. How Do I Figure Out How Many Rafters I Need? Plug Your Measurements Into the Rafter Length Formula It might trigger traumatic memories of high school math class, but the sheer bliss in knowing that you sized your rafters correctly is well worth it.
To put you on par with the experts, we provide the formula carpenters use to figure out common rafter sizing and where to mark cuts.Īll you need is paper, a pencil, and a scientific calculator. Seasoned framers know how to calculate this crucial measurement no matter the project requirements thanks to millennia-old trigonometry. Before building a gable roof or hip roof, you need to know your common rafter sizes.
