It depends on your seat height, whether you are paddling a C-1 or C-2, what your torso height is and how long your arms are. The best way to discover the appropriate length is to sit in a canoe, back straight, lean forward slightly, fully immerse the blade, have your lower hand just above the gunwale and your upper hand just at the top of your head. There it is. I usually recommend a 2″ difference between C-1 and C-2.
By Marc Gillespie, Mar 2008, http://nymcra.org
Sit in a chair and measure the distance from the chair seat to the bridge of your nose or eye-level, this is the length of your shaft and grip.
Add the blade length of the paddle model you prefer in order to obtain the overall paddle length. Overall canoe paddle length is measured in a straight line from the tip of the blade to the top of the grip.