I’m 13 years old, 5’3 110 lbs and last time I threw with a radar gun of the mound was in January, 66 mph, now that our season is in full swing and I’ve grown a bit I’d say I could top out at 68 mph, is that good for my age/size?
At only 13 years old, I would pay very little attention to velocity. Instead, I would work on good mechanics and being able to repeat those mechanics (muscle memory). I would only worry about velocity AFTER you are done growing, and I am assuming you aren’t done growing. Let me know if you have any questions and I would be glad to help.
You are almost the identical size my son was when he truned 13. He was throwing in the mid 70s as a 13 year old. High 60s to mid 70s is very good for that age no matter what your size. As you get older and stronger you will see increases in velocity and control. I cannot stress enough to not overuse your arm at your age. Focus on mechanics and control and keep your innings down. My son is now 15 and is 5 ft 8 and 135 and touches 87 on the gun regularly He pitched rarely as a 13 and 14 year old and worked on strength. mental preparedness and letting his body mature with age. Now that he is in high school and just made the varsity team in Florida as a freshman the patience and maturity that comes with time is paying off.