Calculate Based on Oarlock Size

• 1). Measure the inboard length of your boat, in feet. The beam of your boat is equivalent to the width of the boat at the oarlocks or the place in the boat from which you will be rowing.
  
  
• 2). Add two feet to the length measured above. This yields a measurement of the boat's inboard length.
  
  
• 3). Multiply the inboard length by 25 and divide by seven. This calculation yields the approximate appropriate length for your boat's oars.
  
  
• 4). Consider using oars that are longer than the length calculated above if you plan on rowing the boat for speed or if you plan on using the boat for racing. Longer oars provide more leverage, which will add more power to each stroke that you take. However, adding length may make the oars more difficult to maneuver for rowers who are inexperienced or less strong.
  
  
• 5). Consider using oars that are shorter than the calculated length if convenience is your primary consideration. You can stow shorter oars at the bottom of your boat as a secondary means of conveyance. For example, you can keep a small set of oars in a motor boat for use in tight spots or if the motor cuts out. If you are particularly cramped for space, you can purchase oar extenders that attach to the end of a shorter oar to provide more leverage and rowing efficiency.