The American National Standards Institute (ANSI) sets the standards by which utility poles are classified based on size. The greatest variations in these classifications are in length and tip circumference. But the classifications also incorporate information about load-bearing capability, which is related to size and other factors regarding the integrity of the material out of which the poles are made.
H5 - H1
The "H" classification indicates the largest utility poles in terms of circumference and height. H5 poles can range from 45 to 125 feet tall and are no less than 37 inches in circumference at their tip. The lower the number after the H the smaller the pole. The sizes go down incrementally by two inches of tip circumference. So the H1 is 35 to 125 feet tall, but it is a minimum of 29 inches in circumference at the tip. The horizontal loads that the H-classification poles can hold range from 10,000 lbs. for H5 to 5,400 lbs. for H1.
Just below the H classification poles the scale starts over and goes from 1 to 10, so a Class 1 pole is the next smallest after a Class H1. Class 1 poles range from 35 to 125 feet in length and have a minimum 27-inch circumference at the tip. Their horizontal load-bearing capacity is 4,500 lbs. The sizes drop incrementally down to Class 5, which are 20 to 50 feet in length and a minimum of 19 inches in circumference. They have a horizontal load capacity of 1,900 lbs.
The Class 6 through Class 10 poles are the smallest, and no Class 8 pole exists. The Class 6 poles are 20 to 45 feet in length and a minimum of 17 inches in circumference at the tip. This drops incrementally down to the smallest classification. Class 10 poles are 20 to 25 feet in length and a minimum of 12 inches in circumference at the tip. The horizontal load-bearing weights for Class 6 through 10 range from 1,500 to 370 lbs.