How to Choose the Right Oar Length for Your Raft

Picking the right oar length is one of the most important parts of setting up a comfortable and efficient oar boat. A well-sized oar lets you row smoothly, maintain control in pushy water, and stay strong through long days on the river. 

Some boaters rely on the 1:2 ratio “⅓ inboard / ⅔ outboard” rule to size their oars. It’s simple, easy to visualize, and gets you close. But close isn’t the same as ideal.

A Better Ratio 11:27

A more efficient setup uses an 11:27 ratio — meaning 11 parts of the oar length are inboard and 27 parts are outboard. This works out to roughly 29% inboard and 71% outboard, giving you:

• Better leverage,
• A more natural hand position,
• Less fatigue, and
• Cleaner blade entry and exit on every stroke.

Using the 1.63 Formula for Oar Length

After years of rowing and rigging rafts, I’ve found a simple, fast way to calculate proper oar length:

$$\text{Oar Length}=\text{Width at Oarlocks}\times 1.63\; (+/-\; 6")$$

This 1.63 multiplier builds in the 11/27 ratio, so you end up with the right balance between inboard and outboard from the start.

Example:

If your raft is 66 inches wide at the oarlocks:

• 66 × 1.63 = 107.6 inches
• 107.6 ÷ 12 ≈ 9 feet

That means a 9-foot oar is a great fit. If your raft tubes are big and/or you have great oar management you can bump it up half a foot to 9' 6" oars. If you're oar management is weak or you are worried about the strain of longer oars on your shoulders then drop off half a foot to 8' 6" oars.

This formula gives you a solid starting point, but you can fine-tune depending on seat height, tube diameter, oar management, and personal rowing style.

Setting Your Oar Stops

Once you’ve chosen your oar length, set your oar stops or clips to match the 11/27 ratio.

For a 9-foot oar:

• Total length = 108 inches
• Inboard = 108 x 11 / 38 ≈ 31 inches
• Outboard = 108 x 27 / 38 ≈ 77 inches

For a 10-foot oar:

• Inboard ≈ 34.5 inches
• Outboard ≈ 85.5 inches

This creates a comfortable handle spread, smooth rowing strokes, and efficient leverage.

Quick Reference Chart

Final Thoughts

The ⅓ inboard / ⅔ outboard rule will get you on the water, but if you want to row more efficiently and comfortably, the 11/27 ratio is a better approach. Combine this ratio with the 1.63 multiplier as a starting point for the right sized oar.

A properly balanced oar setup means less strain, better boat control, and a lot more fun on the water.