Dance skirt sizing - can someone help me?

[NoahAndTheWhale]

DD is 5 and average sort of size. Am watching/bidding on ballet skirts on eBay - I am sure she had an 18/20 inch one at previous dance place but there is an 18 inch one that someone said their DD had from 8-10. Am hoping for a little growth room but am confused :)

Bump. With added twirl :)

What sort of skirt? Character or ballet circle/crossover skirt.

My average 4 year old dd2 wears an 18 in the elasticated ballet circle skirt .... My slim 6 year old(nearly 7) wears an 18 in the crossover skirt (has hook and eye fastening).

However the skirt is a bit tight on my 6 year old.

I'd have thought an 18 would be fine on a 5 year old.