A bedroom with a king single and a double door wardrobe would be great for any of these ages.
16 year old girl would so love a double bed, so might need to keep that in mind.
Bathroom..couple of drawers, one basin and a 900 shower and a toilet would be pretty impressive.
If the budget allows and you could have rooms that allow for a double bed, double door wardrobes and a dresser, that would pretty much cover their teens......
Any bigger and they may never move on

Is this for a new build? I think bedrooms with a minimum size of at least 3000x3000 would be best... especially for resale. A standard robe should suit. A main family bathroom (bath, vanity & shower) plus an adjacent powder room (toilet & vanity) will be a wise investment as the kids can have their privacy as well as allowing one to access the shower or clean teeth while one is in the toilet... will save some bickering & fighting with that issue at least :)

I would suggest 3x3.5 m for the room as a minimum, plus the robe. I think anything smaller feels pokey and is hard to furnish with a desk, bookshelf and perhaps a double or queen bed. Particularly as kids tend to stay at home longer these days. Your 9 year old boy might not leave home until he’s a 24 year old man. And try, where possible, to make them all the same size.


I don’t think walk in robes are necessary for kids’ rooms, though the teens may disagree. I think it depends what works in your floor plan and budget. A well planned smaller robe is better than a poorly planned larger one. Double hanging rails are great for shirts, trousers, skirts but some of your kids will need single rails too for dresses. Also think about their stuff. What do they need to store? Toys and games, sports equipment, bags and backpacks, hobby paraphernalia? Will their linen be stored in their rooms or in a central linen cupboard? How much other storage is there in the house? Outside the house?


For the bathroom, I love the floor plan my Mum has. It has separate toilet, wet area (bath, shower, space for drying) and vanity. You can have one person on the loo, one in the shower, and another brushing their teeth at the same time. It also has storage for towels. Its genius, great for the morning rush, but it takes up about 2.7x 3.3m of space. If space is really tight then the minimum you could get away with for a main bathroom/toilet is probably about 1.5x3m but it would be tight. You would either need a shower over bath or to forego the bath. If possible, have a separate toilet and bathroom. It makes for a more peaceful household.


Good luck with the build.