There are way too many unknowns to even attempt to give a meaningful answer. If you are tackling this preconstruction I would suggest making a list of what you expect of this space. Is the room(space) simply a spot to keep a bed in? Will you be storing clothing, toys, athletic equipment, books, a study desk, etc..? How long will the child be in this room? Consider future requirements. What do you expect of the child's room? Will it be somewhere he/she can call his/her own, a place refuge, solace, imagination, and rest? Do not despair if you are in a situation of "shopping" for an existing space or are considering some sort of remodeling. One thing to keep in mind is very important, a room is three dimensional, do not limit your plans to a two-dimensional measure(Floor space). Think of the wasted space you can observe all the time in homes and buildings that goes unused above peoples' heads. That vertical space is even more available when the occupant is not as tall.
a average laundry room is 20 metres
The average laundry room is 110 sf :D
A book case that is no more than 3 shelves high will be safest for a small childs room.
what are the dimensions of a study room
About 100 square feet is the averge room size for a heater to be used.
The average size of a utility room is around 25 square feet. It provides enough room to store a few belongings but not much more.
In the American home, the average size of a living room is about 250 to 300 square feet. The room is generally slightly rectangular in shape.
12' by 19'
27ft by 19ft
There is no information on an internationally average size.
About 20 x 25 is average where I live
Do not buy anything more than a 13 inch diagonal. This is large enough to watch a show, but will not encourage a child to spend too much time in their room watching TV.