The length of your boat oars determines your comfort while rowing the boat. Boat oars that are too short will sit at a steep angle to the water making it harder for you to row. Oars too long for your boat's width will increase the amount of weight extending beyond your boat's oar locks, making rowing difficult. A traditional formula determines the correct oar length for your boat, using the width of your boat--rather than the boat's length--to determine the oar length required for comfortable rowing.

Measure the distance between the oar locks with a tape measure.

Divide the measurement by 2, and add 2 inches to the dimension. For example, a boat measuring 48 inches between the oar locks divided by 2 would equal 24 inches. Adding 2 inches would give you a measurement of 26 inches.

Divide the dimension by 7. For example, 26 inches divided by 7 would give you 3.714.

Multiply the number by 25. Keeping with the example, 3.714 multiplied by 25 equals 92.857 inches.

Convert the number in inches to feet by dividing the number by 12. 92.857 divided by 12 inches equals 7.73. Increase the number to the nearest foot. In the example, the optimal oar length is 8 feet.