what is the right size bike for a 7 year old?

Answer 1

Well, the child's height is more telling than the age. This being said, my 8.5 y/o daughter is small for her age and has been riding a 20" wheeled MTB styled bike for a year now. I'd say a 20" is safe to buy unless he/she is very, very tall or short for their age.

Answer 2

When purchase a new bicycle, have the 7 year old get on, and see if his rear end touches the top bar, if it doesn't and is too low, the bike is too small, the rear end must touch the top bar of the bike, then he will be able to ride it properly.