24:31 contains the dress code for a properly-attired Muslim woman.
And tell the believing women to reduce [some] of their vision and guard their private parts and not expose their adornment except that which [necessarily] appears thereof and to wrap [a portion of] their headcovers over their chests and not expose their adornment except to their husbands, their fathers, their husbands' fathers, their sons, their husbands' sons, their brothers, their brothers' sons, their sisters' sons, their women, that which their right hands possess, or those male attendants having no physical desire, or children who are not yet aware of the private aspects of women. And let them not stamp their feet to make known what they conceal of their adornment. And turn to Allah in repentance, all of you, O believers, that you might succeed.
Way I look at it, no cleavage should be on view. That's it.
A woman's "ornaments" are her breasts and thighs.
Arguably, an ugly woman has no ornaments at all and everything about a beautiful woman is an ornament, including her eyes, which you cannot cover or you would be blinding her. I suppose you could argue that she should always wear sunglasses in a public place, but that would be impractical and extreme.
Having dealt with a woman's upper torso, we now, er, "lower our gaze" to her legs.
Therefore, you have some sort of sensible rule. I would suggest that modest dress includes skirts.
Let us say then that anything above a woman's knee is an ornament, and skirts, to be modest, should cover a woman's thighs.
In one morning I have single-handedly resolved and pronounced upon the proper dress code for all decent, right-minded women, Muslim and non-Muslim, for all time.
In a perfect world, I would be called upon to be the Mufti of Britain.