For Ottertails, Modified Ottertails, Modified Specials and Ray Specials, measure the distance between the floor and your nose. This will provide the length you will need. If we dont offer that specific length in the model you're looking at, you can simply round up or down to the nearest size. Keep in mind if the paddler is still growing, its fine to order 1 to 2 inches longer so they can grow into it. Alternatively you can consult the sizing charts in each paddle product. Quills are designed for Canadian Style Solo Paddling, best sized by determining the shaft length the solo paddler needs. To do so, take your current solo paddle for Canadian style paddling and see how much you choke up on it. Measure where your lower hand pinky lies to the top of the grip and add 1" in length. This will get you the best shaft length needed.