Hi,
Can anyone help me please, i’m wanting to get my 10 year old nephew a unicycle for Christmas. I have looked on lots of web sites for the correct size for him and all have given me different answers.
Could someone please help me out 
Hi Claire.
Have you tried this group
They are located in many countries & will be more than happy to assit you with all your needs.
How tall is he? A 20" should be fine for most kids.
Buy one with a 20" wheel. That is what I did for my 10 year old daughter. If he is on the shorter side you can cut down the seat post, and then later as he gets taller replace the seat post. He will be able to use a 20" his whole life.