The most common age to potty train boys is between the ages of 2 years old to 3 years old.
Most boys are potty trained by age 3 although some boys may not potty train until age 3 and 1/2 years to 4 years old.
Some boys are potty trained as early as 18 months of age but even when you begin potty training at 18 months the child still needs lots of help with using the toilet.
When it's all said and done even starting as early as 18 months the child is not fully potty trained and able to use the toilet independently until age 3 to 3 and 1/2 years old.
If you wait until at least 3 years old the boy will have better bladder control and be more able to get to the toilet on their own and pull their pants up and down and wipe without much or any assistance.
I've always waited until my kids were 3 before even beginning potty training and went straight to underwear without using pull ups.
Once they were 3 my kids both boys and girls all potty trained within a few weeks to a few days.
When you potty train as early as 18 months or under 2 years to 3 years old it's more the parents being trained to take the child to the toilet and remind the child to use the toilet.
If you potty train before 3 you will be dealing with lots of accidents which means in reality the child is not ready.