A 27 inch waist would be a size 10 but your hips are technically a size 12 and bust is a size 14. That is about a size 3/4 or 5/6. Of course the size of your legs and rear could mean that you run a size up or down.
That would also depend on their hips size, but generally a size 6/7 if you have a 27 inch waist measurement. Source(s) But if you mean jeans labelled with sizes 26,27,28, etc, then this is a size 4/5. answers.yahoo.com