What size oars do I need for a row boat?
What size oars do I need for a row boat? The Original Shaw & Tenney Oar Length Formula Divide the span by 2, and then add 2 to this number. The result is called the “inboard loom length” of the oar. Multiply the loom length by 25, and then divide that number by 7. The result is the proper oar length in inches.